It's really not all that funny of a joke to use some tiny symbol to indicate sarcasm that is easily missed. Discussing with people and deliberately trying to piss them off is an ego game and kinda petty. It is basically trolling for a laugh but with none of the style of Andy Kaufman. Sarcasm should be funny by being obvious.
That specific post is perhaps close to home because I think many of us are sick of people who are making serious statements like that like spoiled irrational children. It's all over the world in every topic and its lowering the quality of not just discourse but life.
So yea, sarcasm should be indicated clearly. Note: I have been guilty of this mistake myself, feeling my sarcasm is obvious when it was not.
But no matter how obvious you make it, some people won't realise.