A major part of modding is that the player appreciate the effort of modding (at least for me). If the mod is crap, but nobody criticises or points out flaws, then everyone is denying the modders chance to make his mod enjoyable, and that, I think is a goal all modders have.

If everyone pretends the mod is good, never criticises, never argues, then the modder will never know if he has achived his goals. In my oppinion, thats worse for the modder than being criticised. At least he can change that.

PS That doesn't mean you should grill modders ;-)