Everyone is being unnecessarily rude to you. It really isn’t unreasonable that you wouldn’t have heard of this guy if you are some combination of an American, not a sports fan, and in your thirties or younger. However in his day he was considered one of the two best players all time in the most popular sport in the world. That resulted in a fame that far exceeded the world of sport. He also basked in the life of celebrity that ended up compounding his renown even further. He was probably at one point one of the 10 most famous people on the planet. It can therefore be surprising for people who lived through that time that other people might not be aware of him.

That you hadn't heard of him was perhaps not sufficient basis for feelings of astonishment. I guess it's just surprising to people of a certain age, who overlooked the age/background of yourself and others. But I really don't think it was intended to be exclusionary or make you feel unwelcome. The down votes were probably b/c of the Michael Jordan comment. If there is a rule that every submission must have a tech, science or similar angle, it appears there are exceptions. And most people are OK with it.