Here's one for the straight boys that you can pen down in your grimoires: your view of gay being irreconcilable with actual gay people's views centers around the concept of faggotry.
When straights say 'gay' what they mean is 'faggy' and this is an insular concept that they use to police each other. This one crosses cultural barriers and epochs, too. THOUSANDS OF YEARS AGO the greeks were engaging in behavior that contemporary straight people would call super ultra mega gay. Older Athenian men would mentor handsome younger men (with their dicks) and young Spartan men raised together in fighting units would sleep together and use their love for each other as a bonding force. This wasn't gay or straight, those concepts didn't exist back then, but faggotry certainly did. No one considered these concepts faggy because the men were acting in proper accordance with all social expectations for right and proper Athenian or Spartan men. What they considered shameful and faggy were weak men who'd act as prostitutes or sluts and waggle their hips like some loose woman.
This old paradigm of faggotry is centered around two archetypes: the Macho Man who acts properly and the Sissy Man who doesn't. It's about showing weakness. Sissy behavior is effeminate (not strictly behaviors of women, and in fact they're distinct, but rather anti-masculine behaviors) and this has always been harshly punished and policed by the prevailing social order of the day. In our time it's straightness. Men and women both will bully any man who's acting faggy as a way of convincing him to clean up his act. This is a central fixture in the sexuality of straightness. The gay community has always had to react to straights trying to call them out for faggotry, of course, but that play doesn't work when the person you're using it on is reading from a completely different book.
Gay culture still has the concept of macho and sissy men, of course, but it's a different understanding and the dynamics involved are different. Faggotry there is tongue in cheek, an inside joke, and doesn't define their sexuality the way it does for straights. They have their own sense of what a proper gay man is like and, though they don't call it faggotry, if someone violates it then they will deal with it in much the same way: through course-correction bullying and ostracizing.
Two people from different cultures using the same words are not talking about the same thing.
