The Castro in San Francisco used to be a working-class Irish neighborhood.
Chelsea in NYC was once a working-class Irish neighborhood as well.
Neighborhoods constantly change, they don't stay fixed to the same demographics for long. This article points out that gays have been leaving San Francisco in droves, many have been displaced by incoming heterosexual straight tech couples (and they have kids). Yet a bunch of people on FR keep spreading the false message that SF is all gay. Far from it, as the tiny percentage is shrinking. As you say, the Castro used to be an Irish neighborhood. Same for other districts, like the Mission that used to be all white Irish/German/Italian until recently when hispanics came in. Those same hispanics are now complaining because white tech workers are taking over the "historically" hispanic Mission District ("historically" for a few decades). The white tech workers (including asian tech workers) are cleaning up the city and displacing the trash.