Seems kind of disingenuous to make an app that has similar functionality to a few others, including Secret which in some countries was legally barred due to bullying problems, and then just say it is "up to the users to not bully".

You have to take some responsibility for the things you put out in the world.

Please learn from Secret. There are some things you should choose not to build. This is one.

Secret was an awesome app, it has not only inappropriate content but a lot of cool jokes, stories, news etc. It was closed not because people haven't used it but because it went not the way founders wanted. We don't have over expectations in the field.

My point is that the Secret founders, who thought long and hard about this, concluded that the social cost (harassment, etc.) outweighed the benefits ("cool jokes", etc.). I am imploring you to learn that lesson instead of repeating the same mistakes--and harming others.