It is a belief of some neo-Hindus or modern Hindus that the Rig Veda Samhita (RVS) is the true scripture or foundational scripture of Hinduism, while the other Vedas like the Yajur Veda, etc. are less authentic.
This belief originates from western indologists who say that the rig veda was first composed, then yajus, then sama, and lastly atharva.
Moreover, they also claim that the Samhita portion of each Veda is more authentic than the other portions like Brahmanas, Aranyakas, and Upanishads especially.
From this it follows that the other Vedas have to be interpreted in accordance with the Rig Veda Samhita, and some even go so far as to say that those Vedas have interpolated verses, since the content of those verses is supposedly not mentioned in the RVS.
For example, the Yajur Veda purusha sukta (PS) hymn has extra verses than the RVS PS hymn. In those extra verses, one verse states that Lakshmi is the wife of the Purusha. But since these extra verses are not mentioned in the RVS PS hymn, it is concluded that it is an interpolation.
Second of all, "less authentic" does not mean "not authentic", and so it would still be "authentic". So then why not accept the PS of the yajur veda?
My question is, what is the basis for asserting that these Vedas are "less authentic" than the RVS?
As a matter of fact, no ancient Vaidika or Rishi has ever asserted that the other Vedas are less authentic than the RVS. Scholars like Vyasa, Jaimini, Shabara, Adi Shankara, and Kumarila Bhatta all hold that all four Vedas are equally authoritative since they are all apaurusheya.
So what are the arguments to show that the other Vedas are less authentic than the Rig Veda Samhita?