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Staind frontman Aaron Lewis had a rough Saturday night in front of a raucous crowd, which he didn't help when he threw Latin Americans under the bus ... and walked off stage.

Aaron was performing solo at the Pharr Events Center in Texas Saturday night, where eyewitnesses tell us he refused to play his final song on guitar because the audience wouldn't shut the hell up. It was an awkward scene ... like a parent chastising their kids.

You can hear people in the crowd start to get annoyed by their fellow concertgoers -- and perhaps Aaron himself -- and eventually someone asks him to sing something in Spanish ... which spurred an interesting response from Aaron.

He says, "I'm sorry, I don't know how to speak Spanish. I'm American." Some people in the crowd cheered, others seemed to show their disapproval.

Eventually, when the crowd wouldn't quiet down to Aaron's required level ... he left the stage, wishing everyone a good night. Safe to say, people were not happy about it.