Not sure why you're getting down voted. The OP wasn't explicitly about the US but Bernie Sanders got 13M votes in the 2016 primary and he is very clearly in support of taxing the wealthy. That sure is a lot of "insane" people isn't it?
What is unreasonable is assuming that taxing wealthy individuals is, on its own, enough to solve all these other social problems. There just aren't enough billionaires for that to work.