I had no idea how homophobic many of these socialist spaces on reddit were.

I'm unsure if you're aware, but this is essentially the orthodox thought for a lot of "traditional" Marxist philosophy. Mao-ism and Stalin-ism explicitly state that non-heterosexuality and non-cisgender identities are a direct result of the individual's alienation under capitalism, the individual has become so alienated from themselves they begin to engage in "unnatural behaviors" such as being gay or trans. While Lenin did push for the decriminalization of homosexual relationships after the revolution, the belief was still that it was merely a stepping stone to alleviate the trauma caused by capitalism, and that homosexuality would eventually stop once capitalism was gone long enough for the alienation to subside.

It's why I do not like how often the phrase "read theory" is pushed in a lot of socialist circles: there is, objectively, a lot of racist, transphobic, and homophobic nonsense in older socialist writings that are recommended for people to read. You would think with how many LGBT people are drawn to the structural ideas of socialism that there wouldn't be so much queer-phobia, but such discrimination tends to me more the rule than the exception.