I think there is a little more nuance to it than that. I don't think anybody legitimately believes he did it and simultaneously didn't do it.

There's basically a slider of dialogue ranging from "he ought to have a fair trial" to "he didn't do it" to "if he did it, I'm glad he did" to "we need more Luigis"

People are generally pushing that slider as far as they socially acceptably can for the given circumstance they're in. You're not gonna say the latter things in public or with your name attached out of fear of reproductions.

So what you get is a mixed bag of feelings, which are almost all pro-Luigi even if they're different forms of it.