It's "judging" not "judgemental". It means that we J's try to make decisions based on know facts (at least the thinking ones of us do) and we are not content to just "go with the flow" as are P's.
Judgemental simply means someone in the act of judging. It gets a bum rap like the word discriminate. You do not discriminate when you are being judgemental about legitmate concerns - you are being smart, discriminating, and judgemental.....all good things.