Responding to trolls, whether to argue in a civilized manner or to merely lash out at them is a very human way to react. Since we are human beings, it may be impossible to grow a 100% thick skin against all evil comments. So, no matter what your background and blood sugar level is, following the rule "don't feed the trolls" can seem very, very counterintuitive, even if you are aware and prepared.
With the help of modern technology and anonymity, it is indeed easy to abuse the freedom of speech. However, freedom of speech in itself isn't the problem – it's the apparent freedom from consequences for trolls. This is why options such as blocking offensive users are so very important. Getting blocked/muted/ignored is a consequence! Perhaps a guide along the lines of "Dealing with trolls – what it is and how it's done" should be mandatory reading for all social media users.
I'd like to believe that in cases harassment that only happens online, the victim has all the power and tools to stop it, and that moderators are only needed in extreme cases (threats etc). Things get a lot uglier when cyberbullying goes hand in hand with offline bullying, though.
As for Milo, he could have been a bit more diplomatic, but he never broke the TOS. It's unfair to say that he only measures himself in provocation, as that would imply that he's provocating only for the sake of provocating. On the contrary – he seems like a guy who cares passionately about the things he cares about, and it would be a mistake to measure him in provocation or inches only.