Just another showcase of Mayweather proving how, ignorant, classless, no respect having ass really is. Technically it was legal but have some sportsmanship and fight fair. Dont sucker punch him when he's waiting for the ref to tell them to resume the fight.
You can have all the championships in the world but if you dont have the honor, respect for your opponents or the sport, it doesnt matter how good you are, how many championships you got or your undefeated record. People will hate you.