I don't agree with just letting them be. I think they should be confronted, although just about EVERY SINGLE article I've read on the matter says the opposite. Just ignore them and keep silent, they say. That is news to me though, as I was always taught to stand up to bullies and to stand up for the underdog or the person being bullied and ganged up on.
It's really frustrating to deal with people who are intent on insulting you for no good reason; it happens sometimes and it's usually a group of posters, like a good old fashioned shark feed.
You want to respond to defend, say for the record, that the insult is garbage, but that lets the troll win. So you lose either way. And I've had posts pulled down and even got a warning once for responding to a troll, not trolling myself.
So I guess the trolls are going to win. But if we ignore them long enough, they go away. The only people I've ever put on ignore were persistent trolls and after a few months I take them off and usually that's the end of it