How to submit an application to Google play so that it is not blocked again?

Question

Google Play

Hi all.
One of my apps was blocked on Google Play an hour ago. Application - something like a mobile forum, messages, branches, profiles. At the next update, I received a letter in the mail that the application was blocked. The reason for blocking is erotic content. And to be even more precise, one of the users uploaded this type of picture to design his profile - a girl with a bare back, which the Google Play moderators seemed to consider erotic.
In general, it's a shame, we deleted this picture, and apologized to the user, the new package is ready for download. But in connection with this, the question arises - what to do so that this does not happen again?
After all, we have user-generated content - more than 1000 messages and photos are sent per day, their number is growing. It is impossible to physically check everything, the complaint mechanism for certain messages was available before that. After all, similar projects like pinterest, tumblr, vk, twitter and Google PLus, and even Google search itself, as well as other smaller projects, also contain pictures of various kinds, but their applications do not block.
What needs to be added to the application so that it becomes clear to Google play moderators that this application is user-generated and there may be different content at certain times?
(including prohibited content, and that in this case, not everything depends on the developers. Before that, the rating was 18+.) Perhaps adding a privacy policy
will solve the problem ?
- rules of use (where to state that erotic content is prohibited)?