In Wisconsin, it was legal for him to carry the weapon. And it's legal to defend yourself against possibly lethal attack, as long as you're not the one starting the possibly lethal aggression. And "hey this was really stupid" isn't in this case illegal (sometimes it is, c.f. "criminal negligence").

Maybe the laws are bad, but if you paid attention the laws and what happened (both easy to find out, but not trivial because news sources have been telling their viewers what they want to hear even more than normal on this one), it shouldn't have been a surprise.

Given the setup, the only other option would have been a blatant miscarrage of justice (as defined by Wisconsin). It's not a disgusting verdict.

It's a disgusting setup.