The staff already explained why tapastic set up these guidelines, to comply with the ios and android appstore
Creator who put up their content in someone else's platform like tapastic should follow the guideline that the platform set up, and the platform has every right to change their policy as time change.
Think of it like this, you're bringing your artwork to a gallery so you can gain exposure on your artwork, which probably won't be seen by that many other people if you just hang your artwork on your own home.
If that gallery receives complaints because of your artwork, then in the interest of keeping that gallery open, they have to set some rules,
and they have every right to decide who can be displayed in their wall and who should not,
after all this is not your personal home, this is a gallery which happen to let you put up your artwork there.
If you are a creator who wants to draw nudie bodies, sex scenes or whatever it is that was not considered as okay by the gallery standard, I'm sure you can put those on your own site and put a censored version here, and tell your audience that if you want uncensored version, go to your site.
That way your true audience is not to dependent to the gallery rules, and you can gather your true follower outside this platform and you'll have complete freedom to do whatever you like without restrictions.