Why do people online call nofap a hoax/fake?

Only a minority of population are responsible people. It was always like that. Look around - alcoholicism, drugs, crimes, families splitting even after they have children who need both the parents. But even the things like getting overweight out of laziness is a form of unresponsibility. Watching porn is no different - it's selfish. Not only towards yourself, but also your family, friends, all the relationships you have and ever will have, for the whole society. Only a minority is willing (and strong enough) to push themselves out of those. Try to violate someone's comfort zone when they are not ready to/don't want to move out and you wont get treated as someone who wants to help them, but rather an enemy.
The best thing we can do is to talk about the harms which PMO can bring onto a person, but not push anybody into NoPMO (except maybe for your own kids if you are raising them and want to prevent them from it - but even there you have to explain those things to them too).