I think they have that impression because they really are more progressive in just about all other political issue like the economy, the environment, gender relations, religion, drug legalization, etc.
But when it comes to multiculturalism, I think they're more bigoted. I mean, they have far-right parties rising in power everywhere. As racist as Republicans in the US are, they're nothing compared to what these guys advocate for. They have entire parties made up of Steve Kings over there.
And all this because they can't stand their populations being 5-10% foreign or non-ethnic German/British/French or whatever. I mean, Britain chose to leave the EU and tank their economy because too many foreigners were being let in. Oh no, London is now 30% non-white British!
Meanwhile, just about every big city in the US has been less than 50% white for a couple of decades now.