It doesn't. That's when you ask for thread mediation, or closure, and the hapless member of staff who really SHOULD take out stock in Excedrin gets to explain to each of these people B-Z or whatever that they've derailed a thread, and can they self-edit to at least relate to the OP.
Posting nice is not jumping on them during this and making the matter worse by personal attacks on B-Z. Pretending it's someone you care about helps with that because if you KNEW say, the person you loved most in the world would freak out at the mere mention of dogs no matter what because they had to go through reconstructive surgery to reconnect their face after being savaged by a Chihuahua that resented being forced to wear a tutu, you'd be more gentle in how you tried to convince them that not all dogs are bad, and that perhaps the Chihuahua had an actual grievance re; the tutu. You'd overlook a lot of inflammatory remarks knowing that the person had issues. When you corrected, you'd do it gently, understanding their pain, and not forcing the issues.
I'm just saying to respond, or NOT respond, in love, knowing that someone has something very painful behind them that prompts the overreaction (and I know what you mean, I've seen it, and it's tedious). Know that you don't know who they are, nor what happened to make them that way. Only God knows that, and He doesn't feel we need to know. We DO need to love our neighbour, and there's no "unless he/she is being provoking" clause to get out of that.