Critique is meant to be critical. Constructive critique is an additional

Forums head this way for a couple of reasons.
1- Someone asks for critique. They get it, full fat, no corners cut. The thread dissolves into a defensive tribunal because the person asking for critique didn't really want it, they just wanted some ooohs and ahhhs. Two results. The person posting doesn't post another critique (Or does so in a 'what do you think, not looking for a hard crit' style) and the person who delivered the honest and most likely useful criticism is alienated and, after the initial bashing, can no longer be bothered to respond to such threads in the future as their insight is so clearly not valued)
2- It's the internet. The people on it are not outside taking photos, they are inside on the internet. This will yield a higher proportion of technical, kit-happy people to passionate photographers by default. You see it on every single internet forum out there. There is of course nothing wrong with being a kit-happy techhie (Am am one myself), just don't be surprised to see it take hold of a forum.
I've been burned too many times offering my opinion on people's photos, getting dragged into defensive debates or flat out being chided for my opinion being worthless (Hey, they asked for it...) so it's no wonder I'm hesitant to continue doing so. I don't believe I'm alone here either, which might well help explain the decline in people willing to articulate their opinions on non-technical matters.