Am I sinful for denouncing some, but not all, of those who produce indecent videos, given their large number?

There is no sin upon you for abandoning the disapproval [of evil] if there is extreme hardship due to the prevalence of the evil and the large number of its perpetrators. You can enjoin good and forbid evil to the best of your ability, through emails or mobile applications, by writing a brief advice clarifying the impermissibility of the evil, along with mentioning texts of warning and intimidation.