Back in the day (the '70s) there were still a lot of people who disapproved of homosexuality, unlike these days where it's widely accepted. Anyway, since homosexuality wasn't put up with, especially when a male "came out", some heterosexual men attack the homosexual men on the streets. This was overlooked by authorities because, most likely, they didn't like homosexuals either. So, it was only treated as a minor offense. This was becoming a problem.
That's when the Lavender Panthers showed up. When they came across fellow homosexuals being assaulted, they would quickly become involved and would beat the person (or people) who was involved in the crime, to a pulp.
I'd say that in a way, they had an advantage. No testosterone-filled heterosexual man, back then, would admit to being jumped by a bunch of gay men who call themselves the Lavender Panthers.
