Notes:

Before you start jamming away at the keyboard, just hear me out.

First, I'm not judging Samael as a person. I don't know the guy personally.He could be a perfectly nice guy and, he DID pay 1/5 of the original goal of the kick starter. I just found out about him and his art through website searches.

That being said, the guy was being very naive, and egotistical in my opinion, by wanting his fursona in the game. Not a previously made character or a new one created for the game, but HIMSELF. Toby can get away with that because he made the game. Temmie actually did sprite work for the game and probably is a friend of Toby Fox. But even if Samael paid money, the backer reward was designing a monster for the game, not having a personal cameo. If he and Toby Fox were friends, I'm sure Toby would have done that on his own, but…

Seeing as you have to follow specific steps to even see So Sorry, I'm willing to bet that Toby wasn't happy at being contractually obligated to use a fetish-based fursona.

Edit – Killing "So Sorry" actually ruins your Pacifist run, despite all the rumors saying that it doesn't.

And even though the character is always apologizing or whatever, that isn't real humility at all. That's pretend humility. Otherwise, he would have made a new monster from scratch.

TLDR: Samael should have done what Michelle Czajkowski did and make a brand new monster specifically for the game, not use an uncomfortable fursona based on his fetishes.