I think it would be better to be able to discuss both what we like and what we don't like as long as we can do it without being a jackass.
Only talk about the positive? This place would be an echo chamber.
You completely missed my point. I am not saying we should be all positive, but I am recommending that people talk about the game they like, not the one they dislike, because as MR mentions, it rarely leads to constructive criticism, which is the only good and valid criticism.
I like 4e, I guess that's not a secret. That doesn't mean that I love every single aspect of it, or that I wouldn't change certain things, if I was in charge. And I certainly do not mind debating those things. But I can not do that. It takes exactly 3.2 post on average, and we will have the first telling us how 4e is a video-game, how Rouse stole his girlfriend or how Mearls dressed up as a ninja and ruined his D&D game. Or how WotC can't be trusted, how they lied, or how all their digital initiatives sucks and are vaporware, how Pathfinder is the one true D&D, etc etc, ad nauseum.
That has very little to do with constructive criticism or debating. Where I come from, it's called whining, and it ruins any sort of attempt we have at ever debating and improving D&D.
So yeah, I think it would be better if people stuck to talking about the game they actually like. I am pretty sure we would get much farther than we do now.
Cheers
Edit: removed something that could have been misunderstood.