That depends on the principles. And it is at least unkind to implicate he doesn’t have any. Both of you are making valid arguments, even if they are mutually exclusive. Also, both of you fail to see this from another perspective. It’s like you’re looking at a dice from two sides and argue about which numbers are visible. Sometimes it helps to turn things around and look at them from different angles. I’d bet it would at least improve the tone of this conversation.