Samuel L. Jackson -- Angers XXX Actors - Stop Promoting Free Porn!

Samuel L. Jackson likes his porn ... but he wants it for FREE ... and that's pissing off some XXX stars who accuse Sam of promoting film piracy.

Jackson -- aka Nick Fury -- was at a news conference for the new Capt. America movie when he was asked to name one of the best pop culture achievements of the last 50 years. SLJ had a quick answer: RedTube -- the free porn sharing website.

Now some actors in the skin biz are demanding an apology from Sam ... telling TMZ RedTube is nothing more than a pirate site that allows users to illegally post stolen porn. And, they add, "Superheroes don't steal porn."

Adult actress Catalina Cruz is demanding a boycott of Jackson's films ... saying Hollywood vehemently opposes piracy of mainstream movies ... but somehow thinks it's okay for people to steal a 5-minute porn clip.

XXX actress Tanya Tate says piracy impacts her directly ... because she produces her own web content. "I would gladly send a catalog of adult movies I have directed to Mr. Jackson if he would be so kind as to recant the comment."

She adds, "I have a stack of porn for him to help him see the error of his ways."