I've read far, far worse comments on YouTube and IMDb, that's why I don't read the comments on those sites anymore.
The internet is full of people who snark about things which don't (or shouldn't) really affect them just because they can. That's going to be the case as long as the internet and free speech exist and people have the internet's anonymity to hide behind. But this guy's words aren't causing you to lose money, property or health, and one guy on the internet carping about Nick isn't costing the people who work at Nick their jobs, homes or salaries, so why let him get to you? He's just one guy with an opinion; who cares what he has to say about Nick? If you like what the channel has to offer, then that's all that matters. Who really cares if one adult doesn't like a kids' cable channel? His opinion doesn't carry the weight of sunlight. I'm pretty sure nobody at Nick is losing any sleep over this guy, and you shouldn't either.