Yeah, I think the 'Red scare' thing is a big factor particularly in the US. But there's also a kind of inherent hostility to the idea of a UBI due to our upbringing in the current system. That is, you simply have to work, no questions asked, if you want to survive. This idea that you could survive without having to work is so foreign to so many people, that it will take a while to overcome it.
One of the most handy facts about UBI is that people from across the whole political and economic system support it. It's not a socialist concept. In fact, I think it was the right Libertarians like Hayek and Friedman who were the first to seriously support the idea of a UBI.
I think when people hear UBI, they assume it's the market socialist UBI, supported by jacked-up taxes. That's the main problem.