I read your reply earlier and didn't quite get it, but I think now I see your point.

My response would be that it's okay to unequivocally declare a class of arguments as wrong. "Wrong" in the sense of a bad argument that doesn't hold up, it could still (coincidentally) reflect the correct position. What the author does is different though, he simply declares an entire side wrong on the assumption that they all must be using a certain class of arguments.

But the example you offered does demonstrate an equally important point: There are correct and incorrect reasons to rule out a class of arguments. Clearly "if this were true I'd be bad person, therefore this is false" is one of the bad reasons. The technical term is "argumentum ad consequentiam": appeal to consequeces.

So you're absolutely right to preach caution here.