It seems the once "Great" Britain cannot let go of its grandiose delusions of ruling over and "civilizing" the entire known world.

I've always held onto the suspicion that the distinction between left-wing and right-wing social views is more aesthetic than philosophical. All you have to do is tell a leftist "no", and they turn into everything they hate about their parents.

I don't think the psychology here is one of British world supremacy. I think it's one of moral supremacy where liberals in power think that laws must be subservient to the "greater good". This is pretty common in modern politics actually. People don't understand that government must operate on rule of law, and laws have tradeoffs. A law that is useful to take down mafia might also be misused to take down protesters. As such making laws is much more complex than taking a moral stand. But people would rather morally grandstand than wade into this complexity.