What this particular guy did was dickish. But I have to agree with Dave on this point - this is a problem with social media. Social media attracts the best and the worst of society. If you want to receive only the best, go to church. If you know a neighborhood is populated with gang members, you avoid that neighborhood. But here is a piece of knowledge that you apparently are not aware of - there are assholes in the world. If you put yourself out there for the whole world to see, don't be surprised when jerks join in.