Insulting people isn't really the best way to get your point across to begin with. All that would do is make other people more upset and angry. Not to mention it wouldn't help you get your point across if you just blatantly insult them. Some people are just not going to be open to changing their opinions and you can't force them to change their minds. You can provide your opinion, but as regards to making them change their outlook, that's completely up to them and some people do keep on rose-colored glasses when it comes to nostalgia. Ignoring them if they're just interested in hating the channel would probably be the best option.
As for the question itself, I don't know if I'd say that the channel is over hated. Most of the criticisms I see for the channel are pretty valid, such as Spongebob taking up a good chuck of their lineup and the lineup itself lacking in variety. The only shows that I watch on Nick are TMNT, Legend of Korra and Sam and Cat. If I had Nicktoons, I'd probably watch that more due to some of the show that it airs. It also doesn't help that the channel has a bad history of handling some of its third property shows and they don't give some of their shows a chance, like with Winx Club constantly moving around the schedule. Granted, I don't go to too many other sites where they discuss Nickelodeon, but for at least here, the hatred isn't overwhelming and most of the discussions do point out the channel's strengths and short comings.