If only 25% of American men admit to watching online porn, that means about 70% of American men are liars. (I'll make the assumption that a few don't have internet access and have to look at old school porn in magazines and on video.)
Just 12 percent of online adults said they watched 'adult' videos, with a pretty big gender gap of 25 percent of male respondents vs. 8 percent of female respondents reporting they're watching porn. But since the survey relied on respondents' honesty, Pew notes that 'this may reflect a reluctance to report the behavior among some adults.'"
See that? Even the people doing the study were all like LIARS, LIARS, PANTS ON FIRE. (Washington Post)