"U bum," LeBron James tweeted, assailing President Donald Trump on Saturday for symbolically rescinding the NBA champion Golden State Warriors' invitation to visit the White House, and 658,000 (and counting) retweets later, social media had the most famous four letter-word post since Roger Mason's, "How u." The NFL may have engaged Trump first on his racially charged attacks on the league's anthem protesters, but as NBA training camps opened en masse on Monday, the league's players let the world know that they were ready to join the fight. The NFL is the world's most profitable sport, a $13 billion behemoth. LeBron James, Stephen Curry and John Wall are global stars.