Yes, it's unfair but mostly harmless. They are not directly hurting anyone with their joke. Yes, it could be argued that taking a slot on the trending page removes a slight and temporary opportunity for hard-working comic creators, but that's sort of blaming someone for being successful.
Ultimately, I do not have a problem with people using any specific platform to showcase material not intended for it. For example, Professor Comics (a YouTuber) now has a Pornhub channel also. He uses his PH channel to review comics which contain nudity. This is not the intended content foe PH, so we could hate on him for misusing the platform, but actually I applaud the guy. He's creatively finding a new use for a given resource. I watch his PH videos but not his YT channel. Some Tapas creators should send him their books for review.
Oh! That reminds me of an even better example, Ryan Creamer. This guy was a writer for College Humor. Now he makes safe-for-work videos on PornHub. A typical Ryan Creamer video is "I Hold Hands With My Black GF and Listen to Her Talk About Her Day." The entire running gag is that these are on PH, and it's hilarious. He hasn't broken through into the top twenty performers yet, but if he keeps going, it's inevitable that he will. I say more power to him.