Thing this I never got about Furries, or indeed any online fetish, is why they get into communities and talk about it.
This is super old but I've had this figured out for a while and posted it elsewhere on the forums (edit: I forgot I already posted the stuff in the last paragraph in this thread already): they connect with other people with the fetish
because they could - past tense. To paraphrase Mitch Hedburg, they still can, but they could when they started, too.
In the years before the internet, people with aberrant thoughts such as fetishes dealt with them in one of two ways. Either they repressed them, squashing them rather than nurturing them, or they indulged in them behind closed doors. Society and its norms ensured this.
But then the internet happened. It granted its users two things to an unprecented degree:
anonymity, allowing them to live double lives in what amounted to a new, different world with potential for new, different rules, and
connectivity, which enabled people to find other people with the same interests, fetishes etc. This enabled people to nurture aberrant thoughts that would otherwise be repressed to some degree or other. It can feel natural to behave this way given the opportunity.
On top of all this, the furries are a special case. In the early days of the internet, furries tried to 'break out' into the real world before anyone else did. People outside the fandom pushed back and made it clear that this shit wasn't good. The furries responded by retreating into their hugboxes and echo chambers, creating their own enclosed community. This is why so many furries center their online activities around the fandom. This is also why the fandom is so accepting of other fetishes: they are firm believers in
Geek Social Fallacy #1: Exclusion is Bad.