Check this out- One time the blessed one was staying at a monastery. Now at that time, around five hundred wise guys were in town on business. They discussed the blessed one.
"This shaman says the four varnas are all holy. Surely someone is capable of saying something to him about this?"
At that time there was a student named Assalayana. He was a young high born gentleman, shaveed head. He was tri-vedically literate, liturgico-etymologically educated, articulate. He was a philologist, lexicographer, and an etymologist. He could recite the Vedas in the padapatha style. He was all around cosmologically well versed and displayed the marks of a great man.
Then the brahmins thought.
"Assalayana is capable of debating the blessed one."
So they approached him and begged him to debate about the varnas. When they said this Assalayana thought about it for a moment. He recalled the blessed one.
"I've heard he is a straight talker. Straight talkers are hard to argue with. I'm not able to argue with him about this topic."
The brahmins repeated their request.
"Please. You've lived like he has."
Assalayana refused again.
For the third time, the brahmins asked him to debate the blessed one.