The primary reason those threads probably get downvoted is because they are factually false. This section of the boards is full of proof that they do things about toxic players. If you want to argue about the effectiveness of what riot is doing, then OK, but if you say that riot isn't doing anything then people aren't going to take you seriously since it is blatantly false.
"Ignore him" is only 1 part of the advice and stating it like that is the actual suggestion is disingenuous. You ignore them, as in stay out of the conflict and report them after the game. People aren't suggesting that you bury your head in the sand and pretend that toxic people don't exist.
Those posts are also typically covered in salt as well. You can take the best chef and have him cook the best steak but if you pour a mountain of salt on it afterwards it still becomes inedible.