I get what you're saying. The vast majority of threads on WoW forums are immature, and not well thought out.
Unfortunately, being vocal about an issue is the best way to promote change. Considering the complete blunders Blizzard has made lately, it's no time to quiet down. It may sometime seem like the rational voices get lost amongst the many, many, irrational ones, but they don't always.
A vocal and active community is what has made this game what it is. I'd like it too if the players who come to the forums and vent out of frustration would think a little before posting, but at least they let their frustrations known. That's much better than keeping quiet.