Gay people have long been a target for being otherized and blamed for societies ills (also black people and jews...anyone non white and non-cishet, really). For a while, homosexuality was on a pretty good upwards trend in social acceptance and most open forms of hatred thrown towards them was viewed as very negatively in the westernmainstream, and even anti-gay hategroups tried to keep a low profile and not be too public about their homophobia.

Because of that, Trans people became the new target for the socially conservative, being talked about in the exact same manner gay people used to be talked about. Society wasn't ready for any form of larger trans acceptance and false narratives demonizing trans people took very strong hold in american society recently. The hatred of trans people allowed the same groups who always hated gay people, but now pretended to only be against trans people, to sublty expand their open hatespeech towards gay people again as the LGBTQ label includes both homosexuality and transness. Suddenly, being anything sexually or gender non-normative is receiving strong vocal demonization in the mainstream again, leading to increased hatred and eventually....action. And as we see with the person talked about in the OP, this demonization can affect even gay people themselves, as these narratives can lead to intense self-hatred. And if you're also generally mentally unwell and on drugs already, that's a bad combination.

Ultimately, the reason for LGBTQ hatred is just the fact that there needs to be an outgroup that can be blamed for whatever fits a narrative, so that the general masses can be distracted from actual issues. If your audience is too occupied hating LGBTQ people, they're too distracted to notice that you are actually a fraud and won't rise up against you etc etc. This applies to politicians as much as it does to social commentators who make money off of selling narratives. Trans people acted as a very potent outgroup to rally people up against, and with the success against trans people, now we are seeing attempts to expand the outgroup so it includes gays and lesbians as well, because if your audience is already convinced that one group part of a progressive movement/label like LGBTQ is fundamentally bad, it's easy to expand that impression towards any group within the movement/label.