I work with industrial electrical systems so I see a lot of how things are done "the right way". The amount of horrible bullshit that I've seen in houses that's been done by licensed electricians is staggering. I'd wager for every one dodgy install done by a DIYer, there's an entire house that's been wired in the laziest spaghetti style by a 17-year-old sparky's apprentice and ticked off without even eyeballing it by the main contractor.

A fun way to trigger a dumb argument is to say something about taping (or not) wire nuts.