The actor appeared at The Cabot Theater in Beverly, Massachusetts Saturday night for a discussion with fans of the hit 1975 film ... during which fans are saying he made comments about transgender people -- particularly transgender kids.

Video of the rant itself hasn't surfaced yet ... but, a clip allegedly shot in the lead-up to the convo is floating around on YouTube -- and, it shows Dreyfuss wearing a dress and performing a dance of sorts to Taylor Swift's "Love Story."

Check out the video, allegedly taken before the talk ... it's odd for sure, and though many fans are laughing, attendees online are making it clear nobody was laughing by the end of the talk with Dreyfuss who apparently said people shouldn't listen to kids who say they are transgender and want to transition.

Social media users are saying Richard blasted the Academy Awards' new inclusivity rules too -- not exactly a shock 'cause he's done that quite a bit in recent months. Others are saying he said women are too passive to make big movies work, and some add he took shots at Barbra Streisand and Steven Spielberg.

Again, we haven't actually heard what Richard said, and these are all claims people online are making ... but, they all tell a similar tale of Dreyfuss slamming minority groups -- and, it's not making the guy look good.

The Cabot issued an apology for Richard's remarks Monday, stating clearly they do not endorse what the actor said in any way.