Homosexuality was illegal in England until 1967 and Scotland until 1980*.
Women were not allowed to vote in the UK until 1918 (1928 if you were under 30).
Slavery was legal in the UK until 1833.
All this stuff seems completely crazy now, but none of it is that long ago. What kind of things that are going on now will people look back on and think “what the fuck were they thinking in 2017”? I’m no veggie, but I wonder if in 100 years time eating animals might seem impossibly barbaric.
Alternatively, feel free to add stuff that used to be fine but now isn’t. Anything to pad out the thread, really.
*According to the unimpeachable wikipedia anyway, there’s doubtless a fair bit more to it than that.