You didn't ask me, but it's an interesting question.
I don't think so. Assuming Mangione's guilt as a first condition, the reason he got folk hero treatment right out the gate, regardless of the political alignment of respondents, is because the behavior of Brian Thompson's assassin already conformed to an existing Americam mythos about white and black hats, lone gunmen, the frontier ethic, the distribution of power, and honorable conduct. And Thompson is himself an unsympathetic figure, the sort of person a masked gunman might shoot down and still retain the needed element of honor.
If Thompson's killer had gunned down Thompson's wife, and shot their dog, and had to force another spouse into getting shot to protect a child, nothing of the folk hero mythos would have attached to him.
Also, the Minnesota killer was partisan, went after women, had a kill list, and perhaps importantly, looks creepy and has creepy videos of himself doing intensely religious scolding. That's never going to be a folk hero.