It comes from personal experience. Going through a divorce a couple of years ago, my now-ex-wife insisted that things existed that didn't - all the while screaming that she knew the law. To make a long story short, she toned that down a little when I said to her "I get my advice from my lawyer, a tax attorney, and the Hudson NH police department - not Judge Judy!"

...that and the fact that people seem to like to scream "I have 1st Ammendment Rights" on privately owned web forums.. I wonder if they've ever actually READ the Constitution.....