I have the feeling that this is the ultimate 'feed the troll' reaction. Actually caring enough to track them down, talk to them and reason with them about obviously attention-seeking and ill-meant content? Why?
So as a society, what do you do with such offenders? Freedom of speech wasn't really meant to protect garbage like that. Well, one option is you can publicly shame him, or at the very least engage in a real conversation to see what his logic is. The internet is a free place, but we can't become so desensitized to racism and hateful comments that we dismiss is at part of our daily lives, as nothing to be concerned about. People do end up reading nasty comments, and it does affect them.
If I forget my 'ignore them' position for a second: Either they do violate the law or they don't. If they do, the law is responsible here, not you/we. If they don't, it's a rather weird idea to hunt them down and blackmail them to stop that behavior or you're telling the employer/his wife/his mom about those Facebook posts.
Let's focus on improvements to moderation systems and teach people around us that they shouldn't take random posts on the internet serious.
Secondly, you ( and other people) shape society's culture and norms. Trolling is a matter of culture, not just law, and it is not simply the governments responsibility or not. The people pass laws which the government enforces (or at least that's how its suppose to work in a democracy).
Thirdly, I actually made the same comment as you the other day, regarding "don't take internet comments seriously". Here's a great reply:
I will play the part of the alarmist and also be the first to invoke Goodwin's law by stating that unchecked rhetoric was the first psych-ops that the Nazi's used. Group acceptance of dehumanizing a different group is the first step down a horrible path. It should be checked at every advance. The seed in America seems to have happened with Muslims, as it was acceptable in good company to view them all as fundamentalist psychopaths, the government and media where all to willing to reinforce such group think as it strengthen their case for war, now that the seed has set it has grown to bear fruit. Vilifying or dehumanizing a group of people always leads down a path of darkness. I would not hastily blow it off as being stupid and crap said on the internet, it is a dangerous mindset, that is easily infection to those susceptible to group think and the sewers of it tend to be far too willing to act when they feel emboldened by numbers and the echo chamber.
whether its a garbage or not, that your personal opinion. even if it would be opinion of 99% of population, you would still find people liking his writing.
I am not sure where the problem is: whether it is him writing this stuff, or others unable to ignore his writing. I don't mind trolls; they are sort of a challenge. If someone is smart enough to get intelligent individual involved in the garbage conversation, then its that individual fault. internet is a product of humanbeings and like in real life, there will always be statistical noise, an asshole in the neighborhood, one stupid dude out of 100s your working with, etc.
Checking with Wiki, troll is someone fed off someones responses to his comment. I bet if you ignore this guy long enough, he would stop trolling.