Take this example:
Our first president died today. There was a topic about it and most of the replies on the forums were "RIP great man". However, there were 1 or 2 people who started to involve politics and how he sucked etc...and then a bunch of replies on how saying this is not right (and a lot of "likes" for those posts).
The whole topic got into a stupid argument thanks to 2 "a*sholes". Now, you could say, the mods could remove their posts but again, this is free speech forum.
However, if there was a rating where users could rate other users positive/negative the thread above wouldn't have gone the way it would. Those posts would quickly ruined those peoples reputation and everyone would think again before being an a*sholes .
Why not introduce a simple rating system like on vB. You could also keep the 'likes(thanks)' system and make it so if you click 'like' on a post, that's the same like clicking the green option on vBulletin.
In this forum I'm a member at, where the forum switched to vB to xforo, I've seen a dramatic increase of a*sholes since that update. They know that they can now easily get away and not be penalized.
Maybe my solution isn't the best but there must be something introduced to stop a*sholes . There are even studies (read "The No a*sholeRule") that show that it takes around 5-10 more positive things happening in a relationships than negative in order for the relationship to succeed. I think it's the same on forums. If the a*sholes are 1/10 of the forum the forum is ruined.