Most every group in which membership is voluntary is susceptible to a pattern of behavior that goes like this:
Someone whose attitudes, preferences, or inclinations are, by the standards of the group, iffy or fringe, joins the group.
Having joined, he puts a lot of effort into demonstrating that his attitudes, preferences, or inclinations are perfectly legitimate by group standards.
Having demonstrated this to his satisfaction, he goes on to insist that his attitudes, preferences, or inclinations are not merely legitimate, but positively normative.
Having talked himself into believing his views are normative, he begins decrying the standards of the group as iffy or fringe.
From there, all sorts of interesting things can happen. The group might accommodate him, allowing contradictory understandings of the nature of the group to co-exist. The group might kick him out, at which point he might repeat the pattern with another group, or become a professional embittered ex-group member, or find a group more suited to him. The group might split, with those sympathetic to the fringe member joining him in a new group.
Then again, the pattern might terminate at any point in the process. The fringe member might recognize that he is fringe; he might allow that his views are not normative; he might not think contrary views are beyond the pale.
The only thing that is always a safe bet is Step 1. Any organization that people can choose to join that is not exceptionally careful about who is allowed in (assuming membership can be formally denied) is going to wind up with fringe members.