I feel like the mods need to do two things: 1) kill off stupid, pointless topics faster, before they get totally out of hand by "veterans" flaming and making fun of new members who don't understand that we're a community of mature people (not 13-year-old PSP fanbois), and 2) let the other topics with mature discussions stray a little further from the original topic before closing them. Warnings are totally necessary - topics should never be closed out of the blue without a moderator warning. At the very least, delete seriously offending posts or move them to off-topic (and make a post in the original topic saying that the posts were moved, and link to their new location). There's nothing wrong with moderating the discussions that occur in an online forum.
Slightly OT (but VERY slightly):
What helps me put this into perspective a bit is going back to the origins of the word "forum". Back in Roman times, it was an open area (basically a square or plaza) where people could congregate, meet up, have discussions, etc. etc. These were places where communities gathered and places that communities formed around. I almost feel like the moderation style lately is analogous to the image of a group of people talking in a Roman forum when a Roman general walks in, forcefully breaks up the discussion, and summarily forces people to physically split up and go discuss other things in other parts of the Forum.
(Another analogous situation
Imagine this as well: A large group of students are in a classroom, and the group is having a discussion about some topic or another. In the middle of the discussion, other people start making comments that cause the discussion to go off on a total tangent. The teacher will ask the students to get back on topic, and remind them that they can talk about the totally irrelevant topic later. Another possibility is that they make comments that shift the discussion in a different direction. This is not what the teacher initially wanted the discussion to be about, but it is still an interesting topic and is worthy of discussion. The teacher won't cut off discussion in the name of being on topic, but will let the students continue to explore this different topic. (I'm sure you can all put together the analogy to the current forum situation.)