From my own life: At the furry convention I was last we had a large group of people people show up in front of our venue, I think they followed one of our LGBT attendees, and threatened to storm the hotel and kill all the people (homophobically). Hotel had to lock down it's entrances for the night
There have been unfortunately several situations where Furry communities and individual were at threat and people have been harmed, but it's largely because those communities are also LGBT safespaces.
Or as to describe it in your terms, the effort form a LGBT community is a lot harder to form because of the constant threat of homophobic legislature and terrorism. For the furry fandom, it's communities largely enjoy the comfort of being under the radar due to its nicheness and onlineness.
LGBT is more serious because it's existed way longer than a majority of fandoms, and for the fandoms that are just as old as LGBT most of them haven't experienced as much hardships as LGBT. Legislation was passed as you know that have banned and inhibited the existence of queer communities.
i don't think a demographic is clinical or dehumanising at all? I think of demographics as groups of people with unique needs and characteristics. A fandom is a type of demographic that's usually less serious than something like ethnicity, however there are times when people got harmed over it.
I think I just think of them differently. A fandom is more of an umbrella term. it's something that's less taken seriously than a movement like LGBT (which is fine), both of them have communities in them.
The claim was "nobody is born ever into a fandom" but it has happened, aside from my previous example: definitely a lot of nerds who have children introduce their children to their hobbies. I've met a couple at a tabletop tournament are very big into pokemon and share that with their kids.
I remember in the 2010s fans of popular musicians being harassed. A classmate of mine was harassed by other classmates with very vitriolic language because she was a fan of a then very popular musician. I've definitely received harassment for just not exhibiting any straightness
There are people who've actually been born into a fandom, there were sensationalist stories in the 2010s of babies being raised by parents who are eccentric about Star Wars, some are even named after popcultural things which can sometimes have negative social consequences.