The Bay Area rapper -- who's a big Warriors fan -- was sitting courtside Saturday night in Sacramento's Golden 1 Center for Game 1 of the series ... but, somewhere around the 4th quarter, he appears to have gotten into it with a Kings fan who was sitting behind him.

Per reports, E-40 was standing up a lot and blocking the view of folks a row or two back -- who were complaining. After being issued warnings from Golden 1 Center staffers on hand -- security had to get involved at a point ... which then erupted into a full-blown scene.

As you can see, 40 wasn't happy about the situation ... and was even seen yelling at a Golden 1 Center security guard -- which was also snapped up close for a dramatic photo.

Eventually, the Warriors' guys had to step in and help cool things down ... escorting E-40 from the premises as he continued to chirp with security and fans -- who were mocking him and waving at him as he left. Pretty ugly situation ... and E-40's claiming racism here.

He issued a statement to Shams Charania, saying the culprit was a white woman whom he claims was heckling him throughout the game. 40 says he finally turned around to address her directly, which then spurred security to jump in and only deal with him ... not the lady.

You can go read his full remarks, but essentially ... he says racial bias was at play -- and that despite his success ... he still got the short end of the stick as a Black man. 40 says he was humiliated and that the whole thing was jarring. He also thanks his fans for backing him.