Be sure to read the rule before you leave

I'm just guessing but assuming this is the creators making a direct commentary then I would say X-Rays are for seeing what's inside a person, not just skin deep or by appearances. Liberals and fascists act very similarly at the end of the day so it may be the they're just saying that liberals have a different idea on "the inside" vs fascists. This tracks with my understanding of them, which is that liberals think of themselves as good people in favor of "progressive" values (but not acting on them too quickly!) fighting the good fight for liberation and equality (in some incoherent form, e.g. liberals are usually still pretty racist). Fascists tend to be pretty in touch with their hatred of the marginalized and celebrate violence against them. They still think of themselves as good people but have no illusions about "progress", they are reactionaries that openly want to roll back the clock on various "issues".

But I may be reading too much into it. It may also be that the creators are just making fun of this person, as these characters are depicted in a way to make some criticisms of academic communists. Maybe they're just letting them say something that's both valid in many ways and stupid in some others to suggest their thoughts are unclear.