Getting personal describes a situation in which we stop thinking about the issue and attack the person who is presenting the idea. For example.... "I don't care what he said he's a jerk, I know it, you know it, everybody knows it, so I'm not paying attention to any of his ideas."

Example of someone getting personal in their thinking.

You're such a wimp, you sound like somebody who can't make up their mind. You're not one of us; you're just out to get the kids to like you and you'll do anything it takes; your old man was the same way.