I am an Indian Hindu, I face many situations where there is "Goutra", "Jaati", and many types of class related things are asked.
Are the "class-division" and "discrimination" legitimate in Hinduism??
Yes, as untouchability was mentioned by one of the Main preacher of Hinduism, Sri Adi Sankaraacharya,in His commentary of Vrihad-Aranyaka-Upanishad:
"tasmanna janamiyannaantyamiyanneptpaapaanam mrityumanvavayaniti (Chapter 1,mBrahmana 3/10)"
Sankaraacharya in Mahidhara bhashya writes: tasmat tam antyam janam na gachchet sambhaashana-darshanaadivir na sampeshet.
meaning :Therefore the outcaste should not be met or spoke to nor seen or touched"
A similar explanation has been given in Mahidhara-bhashya for Yajurveda 1/13.(Reference: Omkarnath Rachanavali, Sitaramdas Omkarnath, Mahamilan Math, Vol.7, page 235-236)
Fallen ones are also advised to be avoided in Chandogya-Upanishad(5/10/9)
steno hiranyasya suraam pivan cha gurostalpam aabasan brahmahaa/chaite patanti chatvarah panchamasaachan taih meaning one who ssteals gold, drinks wine, enjoys illegal relation with Gutu's wife and the one who accompanies them are fqallen.(Ibid, page 236).
Mahabharat(Aranyayatra-parva,adhyay 1) syas
seeing, touching, speaking with and sitting together with dishonest people destoys the dharma of people and they can not attain siddhi.(Ibid page 237)
one should not sit beside chandala and other outcastes. if someone eats foods touched by them, they must do santaapana krichchha(austerity).Ibid page 238.
if someone eats rice given by a chandala, he must hve fasting for three nights and one who eats foods cooked by chandalas should have fasting for twelve days (Ibid page 238).
Those who obey these would find these legitimate.
Sri Chaitanyadeva has declared that devotion to God makes all pure:
A chandala who says "Krishna is not a chandala and the brahmin who is dishonest is not a brahmin.
Sri Ramakrishna also says:
A chandal becomes purified by chanting Hari naama(Kathamrita, Udbodhan,page 110, 19/11/1882) and by devotion to God(page 107, 25/11/1882).
Swami Vivekanand rejected the concept of untouchability and so His followers do not obey this also.