People are generally stuck in a shell they call reality, which are actually just stories they tell themselves to make some sense and rules people made up in the past that they grew up with. If UBI goes against some view you understand as reality, then of course you'll say "how dare they think of that". There is talk of property in the other comments here, and a funny thought here: not so long ago, it was entirely normal to own property in the form of other people. Now it's completely not normal because you can't actually own a human being as the reality is that we want all people to be created equal. But at the time, it was normal and if you would question that a slave owner would probably say "how dare you, I paid for these slaves, I own them". But then we reached a higher level as a civilization.

As far as UBI is concerned, I'm just sceptical that it will transform the system. More likely it will be just absorbed by the system, e.g. my rent will just get more expensive and I will not actually be able to work less. Not saying I think it can never work, but I am not sure.