OP is right. The SJW stuff is cringy but other than that they are right. A lot of the comments here say that it is acceptable because they are making fun of the person because that person has a perceived insecurity about penis size or height. Consider these points
What if the guy DOES have a small penis then it's perfectly fine to mock him for it just because he may be insecure about it. Does being insecure make it acceptable to mock that person?
Can we make fun of overweight people because they have q perceived insecurity about it? Like, I'm perfectly fine with it but they are insecure about their weight so its OK to mock them about it?
Can we use 'Gay' as a prejorative . For exmaple: being gay is fine but is it fair game to call someone gay to mock them if they are homophobic? No, it's not because this isn't the 90s anymore.
You can't be consistently body positive if you use height or penis size to mock people. I mean, its still up to you if you do it but don't consider yourself body positive or enlightened in that way if you do. Be better.