V
vinty
A gap of about 20 odd years sounds about right for the disease to take hold, with decriminalization the Gay lifestyle became more open and common, as gay behavior became rampant infections which could be controlled by antibiotics became immune and evolved into AIDS, it is significant that this disease began in a Western country.It's not a gay disease.
A big part of the HIV epidemic started in the USA, so I'll talk about that for now. A lot of the USA when the Aids epidemic really took hold in the 1980's was still very much against gay relationships imo (Even old Regan said it was revenge on gay people, or something like that). Am not even sure if all states had repelled the law on sodomy so your theory about disciminalisation and the rise of aids doesn't make sense to me.
There's another theory that the very reason things got out of hand once the HIV virus had been identified was that 'straight' people were against gay relationships, were homophobic that a lot of gay people kept quiet and didn't seek out the help they needed to, nor take HIV tests. It doesn't sound to me that the USA was 'ok' with gay people on a whole.
In the UK being homosexual (men) was decriminised 51 years ago in 1967. Aids took hold in about 1981. Doesn't add up.