I don't think it's liberal politicians doing this. A right wing person would much rather tend to deny calling something far-right in order to protect their interests. A liberal would scream "nazi" when seeing something that opposes their world view. The nazis have committed horrible crimes and I think that their name should not be inflated, because if - God forbid - the same tendencies would start arising again, you could not use the word "nazi" anymore, because it has been already used e.g. for pro life people.