^ I agree completely. I don't think Walt Disney's guilt would've been a direct influence on the writers, even if they had known about it. Just because they work for Disney as a company doesn't mean they'll automatically know these sort of things, especially since it's quite a personal issue for Walt that he clearly didn't want to discuss. And also, it's too broad of a theory. It's like saying that every Disney parent death that came after Walt's own passing was influenced on his own trauma.
Simba's guilt was a natural reaction that Scar took advantage of, especially since it was heightened because he was only a cub and he knew Simba would be distraught. If Simba hadn't have been guilty after that, he probably would've been worse than Scar.

Seems like a pretty big warning sign of a villain to me.
That being said, I never knew about this. It's a very interesting find.