I don't think that trolling here is very bad compared to the rest of the internet. Sure you can get a troll on any thread now and then, but the serious running threads don't get trolled so much. (Probably because running is pretty boring, even for a troll)
Trolls generally migrate to and accumulate in the non-running and completely off-topic threads. I think they're pretty funny sometimes.
Threads started by trolls typically either get deleted or don't get replies. It's pretty easy to pick out a troll-only thread by the controversial statement in the first post, and no one here wants to troll back and forth forever.
The unfortunate thing is that now I never see good running or training advice anymore. The replies are just from underinformed newbs who read about running online or used to run at school for a few years. Even if there was a good reply, you couldn't filter it out among all of the rest of the junk. You're better off doing your own research to substantiate any info. before trusting the eager-to-reply newb patrol.