Granted, I'm GenX, so my concept of ska is rooted in the 80s, but I can't imagine that it's changed much since then.
Wait a minute... is this one of those deals where it's trendy in some peer group to broadcast a hatred for something? Like anyone who wants to hang with the cool kids has to verify that they too hate ska?
Which would be sort of like pineapple on pizza now that I think about it, so might well be the whole point here...
Probably a bit of that, a bit of friendly taking the shit out of other bands, and a bit of a song taken too seriously by both punk and ska fans. And remember, the song Ska Sucks is a ska song.