George Lopez wanted to shout it out loud on stage with KISS, but the problem was band members were just trying to answer questions from fans ... so George got the boot.

Paul Stanley, Gene Simmons and the fellas were doing a Q&A Thursday on their annual KISS Kruise when Lopez got disruptive, which you see from the video. Check it out ... the crowd begins to boo and yell to take his mic away. We're told George was very drunk.

At one point, KISS manager Doc McGhee leaves the stage because he's so annoyed, and we're told security escorted George off shortly afterward. He was spotted in the crowd sleeping later on during another band's performance.

As for why Lopez was part of the panel in the first place ... he's friends with Stanley and a KISS superfan. We got him at LAX when he returned from the Kruise ... he still gave it a rave review.

We've reached out to George ... no word back so far.