Seriously, What is the Rule on Socks Now?

I'm probably WAY behind on this, but the other day when I worked out at the gym, I saw one of the personal trainers there, a guy in his twenties, wearing black socks with his athletic shoes. Black.

This is unacceptable. People wear white socks with their tennis shoes, right? I was baffled. His black socks were Nike brand, and the white swoosh mark on the ankle displayed to the world that they were not black dress socks. Not even close to the fuzzy black orlon socks worn by great uncle Ned, along with the plaid shorts that rode up into his jackhammer region.

My thin slice of fashion knowledge curled up like a flauta and shot out the window, never to be seen again.

Scott's theory about all this: WE wore white socks with tennis shoes because our dads wore black socks with theirs. And probably their parents wore white socks, etc.

Is this it? Is it all a do-the-opposite-of-that-lame-generation-above-us? I am so lost.