NJ
You wrote:
//I’m not quite sure what beef homosexual people have with society these days (and don’t care) but if they insist on parading through the streets to emphasise their differences (and I can think of no other reason) then they must expect, like others doing likewise for different reasons, to be upset from time to time. Life’s a bit tough sometimes but I’m sure they’ll get over it.//
This is the key area where I think you're slipping up.
Pride is no longer centred on a march or a protest. The protest element has largely died away.
What Pride is now, is more aligned to a carnival. As it has opened out and become bigger, it is less to do with politics, and more to do with having fun.
The fact that London swells by a million people (just think of that!)
This is the thing that I don't think you understand - Pride has expanded to such an extent that it's attended by a lot of straight people. Those who want to have a good time with their mates (straight or gay) in a convivial environment in the sun in summer in London.
I'm sure that even the most dour of us can remember what it's like to have fun, right?