This is definitely not the first time someone has said "Jim/shemps#1 has Music That Sucks, why not start a thread/board that is more positive about music we like?" Sadly, I don't think it will be the last either, despite the fact that I have been neglecting MTS (quick plug: I'm working on a new "induction").
As far as threads go, there are plenty of music threads in the youtube section covering the '50s-'00s and you don't need to only post videos in those, you can discuss shit you like in those. If you disagree with a group I put in MTS you are more than free to discuss that in those threads. As far as forum, as I have said before it is not necessary and Rob has backed me up.
There are plenty of places already to push your "positive message" but keep in mind when you say "I like the Monkees" you leave yourself open to opposing viewpoints and just because I don't like the Monkees (or any other group I might not like) doesn't mean I wouldn't be interested in discussing them.