Ooof! A brave man who separates the historic vibrancy of the forum from the presence of a few quality skeptics.
Theres a pretty simple reality about groups that applies here. Attempts to have discussions in a group beyond a certain size will fail because the conversation cannot be sustained in a way that satisfies most participants. Groups tend to be small - and because of that people will self-select in and out of groups until they find one whose 'vibe' is in harmony with them. And even then that may be the case only so long as a dominant atmosphere remains compatible.
It takes only one individual to render a forum unpalatable and drive others to go elsewhere. My experience has been that conversations are ruined by narcissists, dogmatists and bullies - and many of them have been proud to call themselves 'skeptics' - exhibiting an utter lack of understanding of what skepticism is - and giving it a bad name in the process. That's not to say there are not bona fide skeptics - just that real ones are not so common.
There are some folk who call themselves skeptics who are really only 'skeptical' about a few things, and even so they are not exactly skeptical in the philosophical sense. In essence they disagree, usually very firmly and often without any actual depth knowledge - not infrequently not actually getting the point of the discussion in the first place.
However now and then there are those who are well-informed and who disagree on very good grounds. They have quality arguments. From my experience such folk tend not to piss others off or kill conversations.
Its a hard thing to maintain a discussion among strangers in a way that assures mutual respect and patience - so people self selecting to stay or leave is no reflection on anything really. I am impressed that Skeptiko.com hosts and manages a decent community of people who vigorously participate in discussions - and I have no doubt that other forums are equally impressive.
And some conversations peter out .....................