I wouldn't judge at a hockey game because it's considered a sweater, or a baseball game because it's a button down, but also, the NFL / NBA jersey thing is more & more a social statement.
If you look at the names on the back, half the time it's a social pariah. Some chain wearing, bling bling, gold tooth rapist hood rat piece of shit. What's the message there?
Even back in the day, my childhood, I was hesitant to buy a Warren Moon (rape) or Moss jersey simply because the guy was a fukking clown. Squirting water on refs, hitting cops w his car, destroying local restaraunts w shitty viral reviews, etc.
Then think of where it's gone from there w dudes wearing OJ jerseys, Ray Rice, Ray Lewis, Watson, Vick, Caruth, Kobi, Odom, Thomas, etc
It gives the person wearing it a costume and excuse to act defiant, as if it's an alter ego...it's bad forum and a bad look. It stirs emotions, valid emotions, based on a 4 hour, alcohol fueled experience, in which you turn a blind eye to the morals that preserve a civilized society, to support an uneducated gladiator who serves no constructive purpose on earth or in the community, other that he plays a game.