I guess him being gay isn’t exactly important. The important thing is that the content that he stole was mostly about LGBTQ media studies. So “gayness” is relevant, but strictly speaking his gayness is not.

Edit: I would also note that if the headline writer was just adding “gay” to be incendiary, the writer could have said “Gay youtuber taken down by bi youtuber” but that would needlessly putting in the “bi” label. The “gay youtuber” is “writing” about gay stuff.