He basically started attacking me and several other people who had commented in the post. The conversation is spread across a whole bunch of comments in the post and is very difficult to follow, but here is a snapshot of some of the things he said:

you're wrong, I'm right; deal with, you fucking loser

secondly; you want evidence? read my posts, you ignorant fuck

I tried engaging with him and trying to respond with reasonable replies and questions, but all he kept doing was swearing at me and spewing insults/vague allegations back.

I have continued to talk to him outside of this thread and we are on relatively good terms now. Also for the record, I never actually flagged him.

In my opinion though he was being fairly abusive and inconsiderate to people in the post (myself included).