No, it is without any merit as will be shown in this point by point rebuttal.
Is Buddhism egalitarian?
Let me give an excerpt from Ambattha Sutta, Digha Nikaya:
'So even if a Khattiya has suffered extreme humiliation, he is superior and the Brahmins inferior. 'Ambattha, this verse was
pronounced by Brahma Sanankumara:
"The Khattiya best among those who value clan; He with knowledge and
conduct is best of gods and men."
'This verse was rightly sung, not wrongly, rightly spoken, not
wrongly, connected with profit, not unconnected. And, Ambattha I too
say this:
"The Khattiya's best among those who value clan: He with
knowledge and conduct is best of gods and men."
Ambattha Sutta: About Ambattha Pride Humbled in The Long discourses of the Buddha translation of Digha Nikaya by Maurice Walshe
I have an image of the text below to clear up any confusion.

I am posting here Walshe's summary of Ambattha Sutta
About Ambattha (Pride Humbled). Pokkharasti, a famous Brahmin teacher,
sends his pupil Ambattha (supposedly fully trained in Brahmin lore) to
find out if the 'ascetic Gotama' is the great man he is alleged to be
(and if, therefore, he bears the 'thirty-two marks of a Great Man').
Ambattha, proud of his Brahmin birth, behaves stupidly and arrogantly
towards the Buddha, and thereby learns a thing or two about ancestry,
besides being made to realise that the Khattiyas (the warrier-noble caste) are superior to the Brahmins. Humbled, he returns to
Pokkharasti, who is furious at his conduct, hastens to see the Buddha,
learns that he does indeed bear the thirty-two marks, and becomes a
convert.
A summary of the thirty-four Suttas in in The Long discourses of the Buddha translation of Digha Nikaya by Maurice Walshe
Does Gita defend any killing?
Gita does not support pacifism in situations where one is facing oppression. No amount of pacifism will stop a Hitler from his oppression.
Yield not to impotence, O Partha; it is not worthy of thee. Shake off
this paltry faint-heartedness and arise, O Parantapa:
Gita 2.3
The answer of a hero to hero, shall we say, but not that which we
demand rather that he shall encourage always gentleness and saintliness and
self-abnegation and the recoil from worldly aims and cessation from
the ways of the world? The Gita expressly says that Arjuna has thus
lapsed into unheroic weakness... because he is invaded by pity... Is
this not a divine weakness? Is not pity a divine emotion which should
not thus be discouraged by harsh rebuke? Or are we in face of a mere
gospel of war and heroic emotion... The Teacher himself enumerating in
a later chapter the qualities of the godlike nature in man places
among them compassion to creatures, gentleness, freedom from wrath and
from the desire to slay and do hurt, no less than fearlessness and
high spirit and energy. Harshness and hardness and fierceness and a
satisfaction in slaying enemies and amassing wealth and unjust
enjoyments are Asuric qualities; they come from the violent Titanic
nature which denies the Divine in the world and the Divine in man and
worships desire only as its deity. It is not then from any such
standpoint that the weakness of Arjuna merits rebuke..........
There is a divine compassion which descends to us from on high ...
This compassion observes with an eye of love and wisdom and calm
strength the battle and the struggle, the strength and weakness of
man, his virtues and sins, his joy and suffering, his knowledge and
his ignorance, his wisdom and folly, his aspiration and his failure
and it enters into it all to help and to heal. In the saint and the
philosopher it may cast itself into the mould of plenitude of love and
charity; in the thinker and hero it assumes the largeness and the
force of a helpful wisdom and strength. It is this compassion in the
Aryan fighter, the soul of his chivalry, which will not break the
bruised reed, but helps and protects the weak and the oppressed and the
wounded and the fallen. But it is also the divine compassion that
smites down the strong tyrant and the confident oppressor, not in
wrath and with hatred, - for those are not the high divine
qualities...
But such is not the compassion which actuates Arjuna in the rejection
of his work and mission. That is not compassion but an impotence full
of weak self-pity, a recoil from the mental suffering which his act
must entail on himself... and of all things self-pity is among the
most ignoble and un-Aryan of moods. Its pity for others is also a form
of self-indulgence; it is the physical shrinking of the nerves from
the act of slaughter, the egoistic emotional shrinking of the heart
from the destruction of the Dhritarashtrians because they are 'One's
own people" and without then life will be empty. This pity is a
weakness of mind and senses ......
Commentary on Gita 2.3 by Sri Aurobindo
Does Gita defend the caste system?
Gita's Varna system has nothing to do with the caste system.
According to the aptitudes resulting from the dispositions of Nature
(gunas) and works (karma), the social order of fourfold division has
been created by Me. Though I am their originator, know me to be an
agent but the spirit unchanging.
Gita 4.13
Caturvarnya or the social order of fourfold division is not the caste
system, which is a system of social grouping solely based on birth.
Brahmana, Ksatriyas, Vaisyas and Sudra, as conceived in the Vedas, is
a division based on the natural constitution of man arising from the
dominance of Sattva, Rajas, and Tamas, the constituents of nature
(Gunas), as also on the duties they are fit to perform according to
the aptitudes arising from their constitution. They are mere character
types. …………………..
Commentary on Gita 4.13 by Swami Tapasyananda in his English translation of Srimad Bhagavad Gita
O great hero! The duties of Brahmanas, Ksatriyas, Vaisyas and also
Sudras have been divided according to the quality born of their own
nature.
[Gita 18.41]
Serenity, control of the sense, austerity, purity,
straight-forwardness, knowledge, insight, and faith in the Supreme
Being - these are a Brahman's duties born of his own nature.
[Gita 18.42]
Prowess, splendor of personality, unfailing courage, resourcefulness,
dauntless in battle, generosity, leadership - these are a Ksatriya's
duties born of his specific nature.
[Gita 18.43]
Agriculture, cattle-rearing and trade form the duty of the Vaisya
springing from his own nature, while the natural duty of a Sudra
consists in subordinate service under others.
[Gita 18.44]
A great doctrine of the social philosophy of ancient India, regarding
the fourfold class system, is here propounded. There has been no
doctrine so much misapplied, misunderstood and misrepresented as this
doctrine. The four Varnas of Brahmana, Ksatriyas, Vaisyas and Sudras
are today and for a long time past, understood as four hereditary
castes. But the Varnas, as understood by the best Indian thinkers, are
not castes based on birth in particular groups, but character types
based on the domination of the Sattvika, Rajasika and Tamasika
elements entering into the constitution of their body-mind, and this
is determined by their evolution in their past lives. At least such is
the Gita view. To have identified character types with endogamous
castes is nothing but an aberration. …….
These four character types are universal all the world over and the
prosperity of a society will depend on the man of the right nature and
character being put to the right type of duty. For the individuals
also doing the duty that is natural to his psycho-physical
constitution, is the way of higher evolution.
Commentary on Gita 18.41 to 18.44 by Swami Tapasyananda in his English translation of Srimad Bagavad Gita
Timeline of Mahabharat War
Mahabharata war took place around 1300 BCE almost 800 years before Buddha. Is Ambedkar suggesting that Sri Krishna anticipated Buddhism 800 years before Buddha? I am not suggesting here that the Gita was composed in 1300 BCE. Gita may well have been composed after the time of Buddha. What I am suggesting is that the author of the Gita would know that it would be anachronistic to make the Gita talk against Buddhism since the event described in the Gita predates Buddha by centuries. This is the reason why no one has been able to show any direct argument in the Gita against or for Buddhism.