The award ceremony took place last night in New York, said The Hollywood Reporter.
"You think you've got it bad, LBGT community? I don't think you know what it's like to be really discriminated against," De Niro quipped upon taking the stage.
Making a reference to Marco Rubio's "small hands" comments that fueled the feud between the former candidate and Trump, De Niro said, "I recently turned on the television news and saw this odd guy with little hands, and he was raving. Turns out, the ones being discriminated against are straight, middle-aged white men."
"It makes sense. I've been losing parts right and left to what used to be called 'diversity actors,'" he said.
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"One that really hurts, seeing the role of Dr Dre in Straight Outta Compton going to Corey Hawkins. And I can't remember the last time I got a Teen Choice Award... It's not easy being a straight, white man."
Ending his speech on a more serious note, De Niro, 72, left the audience with empowering words on the importance of supporting LGBT rights.
"I was fortunate to grow up in an atmosphere where freedom of expression in art and in life were the norms. Now, we have to look outside our bubble to the world where, because of religious beliefs or ignorance or mean-spiritedness, it's not so easy."
He concluded, "I'm proud to stand with you. I'm GLAAD.