"Announcing 'I'm offended' is basically telling the world you can't control your emotions, so everyone else should do it for you."[1]
There are legitimate sources of offense, but "bro, you're totally harshing on frats" is not one of them.
The reddit post is applicable because it is a rejoinder to those who claim offense at that which cannot reasonably be claimed to cause real offense to those for whom such a thing matters.
"They're drunken twenty-something white guys whose primary concern is..." <--- Stereotyping. Generalizations. Right here. In your comment.
There are fraternities and sororities whose members are not all "twenty-something white guys" and whose efforts are worthwhile. Do a smattering of research and you'll discover this.