Ninja -- the most famous pro gamer in the world -- is sick and tired of people treating his sport like it's a joke ... and he's invoking the names of LeBron and Tom Brady to make his point.
The 28-year-old Fortnite legend went on a passionate rant while streaming on Wednesday -- saying he's fed up with people telling him to tone down his competitiveness with comments like, "It's just a video game."
Ninja HATES that phrase -- explaining how EVERY top competitor in any field should HATE to lose no matter what sport they're in.