You kind of have to put on a show of cooperation to find mafia in public, but the vig can take out the other town in secret without having to answer or apologize for it. At least vigging people in your own universe is incredibly risky, because there's a high chance of killing your own team, so it's probably best for the vig to focus on the opposite universe. The opposing town needs to be eliminated somehow, and the vigilante is the easiest way to do so.
This is what I disagree with I guess. This is a 4 sided game yet people still bring over their regular mafia ideas. As long as you're not lynching a member of your team, there's nothing to apologise for or explain as far as I'm concerned.
Vigging blind does suck though since there's a big chance of hitting your own team like I did. Unfortunately, I just don't have the time these days to attempt serious networking which probably hurt my team quite abit.