I was told by a dentist to brush my teeth before eating. So at least one dentist would disagree with that I guess?

One reason we brush our teeth is to apply a protective coating. Brushing your teeth immediately after eating can damage your teeth.

A more appropriate analogy is asking whether you’re jumping in a pool of mud before waxing your shoes.

Teeth and ass aren't the same thing and that's not an equivalent comparison considering multiple people have pointed out that brushing before gives a protective coating or at least is less damaging since there aren't food acids present, softening the enamel. A quick google search confirms this.

What, you don’t do it both before and after?

It’s just like showers, you take one as you get out of bed, and another one right before going to bed.

Some people are just dirty, sheeesh…

Edit: -> /s