Avengers star 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 recently asked to name one of the best pop culture achievements of the last 50 years … and 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.”