Here we go again with the laziest possible transaction in political conversation. Find a reason to call someone a racist / fascist / furry and enjoy that hit of sweet self-satisfaction.
ECs / EU membership has been a subject of political controversy for 45 years, ever since we joined. Britain has always had an uncomfortable experience of membership, and there’s always been a large constituency who just aren’t reconciled to the regular, ratcheting transfer of sovereignty. Made worse by the fact that British entry into the ECs was economically and financially painful (and some of that pain was deliberate), and that the British electorate has had an almost permanent misunderstanding of the purpose of the Treaty of Rome because British politicians who most wanted to join were (in general) too cowardly to talk honestly about why.
The 1975 referendum was called because a new Labour government couldn’t resolve its own internal divisions over Europe and a “people’s vote” was the political cover needed to stay in (how different things were then…) In the eighties and nineties Europe generated multiple political crises, sackings and resignations of cabinet ministers, a major financial crisis and the fall of Margaret Thatcher. Divisions over Europe then hamstrung the Major government and continued to rile the Conservative party in opposition.
UKIP (initially with a different name) was formed in 1991, and competed with a Referendum Party for anti-EU votes.
During all that time, Immigration and racism were a long-running background thread in British politics, but not a top-five issue for voters in polling. Immigration only became the top-two issue it is now, around the turn of the century, and the trigger event was the influx of white Christian Europeans. Islam was not on the political radar until 9/11 and the follow-on attacks.
A referendum on membership has been the subject of serious campaigning for 25+ years. IMO it’s been a political inevitability, because that constituency of Euro-sceptics has consistently grown over the decades, and because - as the paralysis in Parliament is demonstrating - it’s an issue that cuts across traditional party lines in a way that’s made it hard for either of the two major parties to build consensus or exercise leadership (the Blair / New Labour period being the exception).
But never mind all that. Let’s just throw in a few smug one-liners.