Richard Dreyfuss' transphobic rant was seemingly premeditated -- 'cause the guy was at a store right before he hit the stage and was trying on dresses ... and we got the video.
TMZ has obtained surveillance footage from the end of May ... showing Richard being helped by a number of staffers at Worthy Girl Consignment in Beverly, MA -- where he later got onstage and made a number of controversial remarks, including against trans folks.
As you can see -- the employees are seen helping the Oscar winner as he tries on 5 different looks ... smiling and laughing with those in the store before finally picking one.
We're told Richard ended up staying at the consignment shop for about 30 minutes, eventually settling on the floral blue dress he wore onstage -- which our sources say is from the plus-size brand Torrid and cost $20.99.
As we previously reported ... the actor then made a controversial appearance at the Cabot Theater later Saturday evening ... where he stepped out in the dress in question before going off on a tirade about the trans community -- among other inflammatory remarks.
Now, Worthy Girl Consignment is seriously pissed off ... with an employee telling us that the actor's rant insulted their main clientele -- the LGBTQ+ community, which they're shocked by.
The employee adds they thought RD was just a cute, little old guy trying on dresses -- and they never could've known he planned on any of that.
It's interesting ... of all the stores in Beverly, Richard selected Worthy Girl Consignment ... as the business makes it clear they're pro-LGBTQ+ by hanging a Pride flag on its storefront.
Whether or not Richard realized the irony at the time remains unclear. Anyway, we're told the store is capitalizing on this controversy for a good cause, designing a Pride shirt referencing the incident -- with proceeds going to the North Shore Alliance for GLBTQ+ Youth.
We've reached out to Richard's reps ... so far, no word back.