Wandering Adventure Party

What template was he using before?

Partially. I think its fine to have that kind of thing. But not all the time. Bandits who are actually good people will avoid murder if possible. And while bad people can also have loved ones, that does not invalidate self defense.

Just as you said: Self defense is not murder-hoboing. If we are talking murder-hoboing then we should apply that list to city guards and commoners, who are not meant to be fought.

I get you wanted to do it for fun, but you sound like a horrible player to have at the table. There is a social contract involved in playing DnD and while disagreements between party members are all fine, your character was basically hindering the other characters at every step (at least from what you described).

While it has nothing to do with the first point: I also reject your interpretation of alignment. It’s (at least from how I see it) not that you choose an alignment and then build a character around it, but that you build a character and then classify them with the alignment that fits their actions best. I know that some classes require certain alignments but even then there are a multitude of different ways to go about that alignment.