Well, I don't know that I would go THAT far, but if someone uses bar-room tactics with me then certainly it should be okay (and necessary for debate) for me to respond in kind to THAT person. The problem with 'others' is that if they get caught up in the maelstrom they can catch 'friendly fire'. It's just too difficult to switch tone back and forth for each post depending on who the poster was and precisely what they've said to you previously. To me, this is all about Machiavellian debate. It's what you have to do to WIN. Nothing personal, just what's required. As soon as the FIRST person gets out of line, the door's wide open. That's what Calculus guy did.
This is why I've always questioned the value of sports in "building character" at least the way it is practiced today. Too many people have this hockey player mentality of intimidation and pressing against the rules. The attitude tends to spread into civilized society.
But you don't win an argument by driving people into silence. You can only win it by being right. But if you become Mr. Kickbutt during a debate it becomes much more difficult to admit it when you are wrong. People like that become Democrats. They have gone over to the Dark Side. They believe there is no such thing as truth.
And Democrat scientists can do more damage than you can possibly imagine.