You can’t shoot somebody standing in a public street unless he’s armed and threatening you. The fact that you disapprove of the WORDS coming out of his mouth, is no justification. Had the man acted properly and they came onto his property after them, it would be different.
You find it acceptable because you’re offended by the words.
Name calling is not a life threatening attack. If the home owner believed an attack was coming by an armed group, why would he expose himself to attack at the end of the driveway? I would have defended from inside the house, where I could return fire from cover.