Company responsibility

Thinking about company responsibility.
Twitter estimates Donald Trump to be worth about 2 billion. While Twitter has allowed Trump to tweet about whatever he wants, even when breaking Twitter policy, they may become the first social platform used to declare war. "The North Korean government claimed the tweet was a 'clear declaration of war,' and a case could easily be made that it broke Twitter's rules prohibiting harassment and content that incites violence." Twitter has been struggling to crack down on harassment and inappropriate content with its rising 328 million users (active accounts).
Youtube has even more users, considering that you don't need an account to view the web content. Its recently come into light that many sexual predators have been using Youtube to recruit children under the guise of a Modeling Agency. Not to mention the overwhelming amount of harassing comments that people leave on videos. Others solicit illegal services, upload inappropriate content, and throw a bunch of internet trolls onto the list. It just makes me wonder if these companies are taking the best approach to monitoring its users, or if it comes down to an individual's moral obligation to not muck up the internet for kids. Or should kids not be allowed access these places, does it fall on the parents to be aware of these issues?