This logic is not applicable for entire tamil nadu, it applies only on southern tamil nadu. In chennai people will use loose tongue against elders, thats normal over there. But in sothern tamil nadu every single word counts while discussing with an elder. When my cousin came to chennai first time he wasn't used to chennai slang, so he thrashed a chennai guy who made a loose talk and got arrested. It's not the mistake of both, in chennai it's ok but in south it's an offence and the police officer warned him to leave chennai if he is not able to tolerate the chennai slang.
Yes caste/ethnicity is much more intense in TN than religion. It's not happened because he is a dalit, it would happen even a maravar guy walked like that. Only in the two districts tuticorin and tirunelveli, Rivalry still going between thevars-nadars, thevars-dalits, nadars-dalits, these three castes are fighting with one another for a long time but no one will ally against or with anyone.
Yes it happened due to caste, but my point is it's not happened because he is from the lower caste.