There are all kinds of reasons why people should be afforded the opportunity to remain anonymous on the Internet, and social media websites in particular. On balance, neither do I think people should be required (by law) to produce an ID to join such sites (though, individual platforms could have such a policy if they so desired - but I, personally, would argue against it). Any site which requires an ID would also have to ensure that the ID data never leaks (we know that websites regularly fail to ensure this).
The problem is that is that it expedient to enforce standards only where there is a legal requirement or where there is a financial benefit. If a huge percentage of your most active (revenue-generating) members are obnoxious and only use your platform because they are allowed to be obnoxious (and the owner is Mark Zuckerberg), guess where the line will fall. As @Gnurglan commented previously, social media is a recent phenomenon - like all new technologies and modes of communication, it takes time to iron out the wrinkles. Either FB and Twitter (and Youtube for that matter) will clean up their acts (enforce some reasonable standards of behaviour), or they will eventually fade away. I don't think the present situation is indefinitely sustainable. When enough people demand something better from their online interactions and leave FB et al, and all that is left is an increasingly dense soup of shit, even the remaining arse holes will grow bored (after all, their sport will have disappeared) and stop participating. I am not suggesting that this is what will happen. Rather, I expect that these platforms will act before reaching crisis point - there will be re-balancing at some time. But, it will the the bottom line which dictates their actions and when they act.
I think there are things which can be done to force their hand through regulation. Obviously, Russian meddling in the US elections, Brexit and (attempts) elsewhere needs to be regulated somehow. The most effective way will be through tough financial (and/or criminal) consequences for those allowing specific activities to go unchecked. FB and Twitter have abdicated all responsibly to ensure even the most basic standards of decorum which is required in the real world and have allowed their platforms to have become propaganda machines. They know this, but it is more profitable to not only do nothing but, actually, in their interest to encourage it (this will change).
@GreatEx I am active at another forum where there is no rating system. I think an effective rating system may be possible (and some platforms do it better than others), but it is difficult to prevent gaming and unintended consequences. Certainly, simple 'likes' can be problematic.