Nope you are wrong. The vast wealth that purchased those houses underpinned the industrial revolution that made those glorious artefacts, employed Capability Brown etc. was all accumulated on the backs of people torn from their homes, treated less than animals, bought and sold and killed in their millions.
I agree, and would also agree with this being made known at the relevant properties.
I don't think that this is remotely the same as expecting volunteers to dress up or wear glittery body paint, though, which is the crux of the thread.
Showing visitors how much of the wealth of individuals in the UK was built on slavery is one thing, but compulsory fancy dress is quite another. I'm confused as to how the two things are being conflated on this thread.
Further, whereas Pride is clearly a fun, loud, glittery, camp event, not all gay people fit that stereotype, and some would (and do) argue that it is counter-productive, and long for the day when being gay doesn't carry those connotations.