Programmers could make 1000 great AI sites, but it will only take a few bad ones to earn enduring hostility from society to AI (and forums that promulgate bad anti-social uses of AI).
Porn objectifies all women (and men), reducing everyone's ability to have real relationships by setting expectations and creating doubts about your partner's real objectives. That makes life unsatisfying, and dissatisfaction bleeds into all aspects of public participation, from politeness through voting and work collaboration. #MeToo systemic bias and oppositional incels are already driving forces in office and partisan politics.
Porn is not illegal, and some argue it's sex-positive. But assuming you are exporting some social costs, even if you were willing to take responsibility for the damage you cause, you couldn't.
It's not fair to force others to clean up after you. And it's not fair to saddle other AI uses with constraints born of misuse.