The Joke starts with a question in the format what is the difference between A & B where one of these A is to be the Butt of the joke. The answer then says one is X where X is a number of qualities, probably laudable, obviously describing A, then the punchline is the description the other is Y with all negative qualities in such a way that you realize that the previous description of X which you thought was referring to A was actually referring to B and the negative Y is a particularly mean spirited description of A. One common variant if you have the negative Y values described first you will just say 'Well one is Y (all negative values) and the other one is A (just repeating the name)'

The comment was written in such a way that it functioned like one of those jokes. I unfortunately cannot think of one of these jokes right now, but for an example of how the reversed version works you might have something like this:

What is the difference between X and Ted Bundy?

Well one is an insane Republican murdering abuser of women, and the other is Ted Bundy.

No particular person was thought of as being represented by X when this example joke was formulated.

You can probably find some examples here https://worstjokesever.com/difference although I wasn't able to - warning the first joke is racist.