Intent surely matters. It should be clear to everyone, even Nick Blackburn's mother, that these comments are playful and not at all mean-spirited. While everyone wishes him health and happiness in his personal life, a little bit of guff from the peanut gallery is part of the price of being a public figure, a millionaire, and poor baseball player.
This is blunt,but not classless: I can be sad that Nick got hurt, but I can also find solace that he won't be pitching for my favorite baseball team and other, better players can be given a chance to play. That's not shameful. It's honest.
I think you're right that intent matters. I also think, however, that while some indeed are playful, that it is quite obvious that other comments are absolutely mean-spirited. Some have been deleted from this thread and there are many in other threads on this forum. And while this may be part of the price of being a public figure, that doesn't mean it should be, or that we all have to think that it's cool or even OK.
As for blunt vs. classless, I don't think those descriptions are defined objectively enough to be able to say definitively that one applies and the other does not. Beauty is often in the eye of the beholder, and so is ugliness.
Full disclosure: I am not Nick Blackburn's mother.