A pragmatist does what works. If it’s not known what works, he experiments. Like a scientist, he makes it up as he goes along. Yes, that’s what good scientists do. Part of what they do, at any rate.
A legalist does what the law says. What the law says is what a bunch of other people - most of them long dead - made up as they went along. That’s part of the scientific process, but there are other parts. The other parts are kind of important. A legalist doesn’t appreciate the importance of the other parts. He fails to grasp the difference between a scientific hypothesis and a scientific conclusion, or the steps that lead from one to the other. And he can’t even be bothered to come up with his own hypotheses.
A lot of people are like that.