It's not about immature people being unable to separate art from artist because it's difficult. The issue is whether it's the right thing to do.

I feel pretty confident that I could describe to you a case (either real or hypothetical) where you would reject an artist based on their personal behavior, rather than their art. You would find it quite difficult in such a case to separate the two.

So the question is where to draw the line, and everyone answers that question differently.