Lot's of people (well, maybe hundreds or thousands) get scammed via ponzi that use Bitcoin as its name. They blame Bitcoin but not their stupidity and the ponzi scheme.

The most famous argument that I heard from people who hate crypto is: the money came out of nowhere, it's a scam and you'll lose your money, it's a bubble, "I invest but then lose all of them so it's a scam", and so on.

So in short: they hate it because they lose didn't get rich quickly.