What does "gay" mean in Britain?
Just a vague nightclubbing category, a guy telling us he's a regular guy.
There's some dude with an earring picking up the ladies. The English flag is not "gay" but there are plenty of patriotic men who are sick and tired of foreign servant girls in the country and continually fighting their false rape charges in court.

He met his fellow flaggers through his online handle “Stevenage Patriots” and had never met them before, he said. “I’m gay and a lot of my friends are girls, so I was quite nervous hanging around with four straight lads,” he added. “But it was such a lovely evening, quite spiritual actually, quite calming.”
I wouldn't make any judgments. The guy has a few too many girlfriends and maybe he's hanging out with a better crowd than he used to, and he suddenly finds out he has a lot enemies he didn't know he had.
If a guy dumps a "gay" boyfriend and people are throwing Molotov cocktails at him, I'd say that's a little bit too much of a drunken barroom crowd altogether, and acronyms such as "LBGTQIA" should be interpreted as a matter of fact that "people are having sex" generally without being too specific or getting into the details, 99.9% straight as it is what it almost always is naturally.
Biologically and instinctually, humans among other animals are attracted to the opposite sex as potential mates, and view the same sex as competition for mates. Biologically, the LGB can be eliminated along with the T, if people are in denial of their biological sex and/or their biological attraction to the opposite sex.