This might be incredibly pedantic, but since this is a mathematical philosophy article, I'm going to go ahead.
These aren't "hard" problems, they're simply questions that don't make sense. Is finding an odd number that is divisible by 2 a "hard problem"? I don't think so, it's just that it turns out that it doesn't make sense to ask the question.
Some of these "hard problems" actually have solutions that demonstrate they aren't solvable, and these solutions are fairly elegant, in which case I'd also say these are not "hard".
I think that's the joke of the title, though; perhaps rephrased slightly: "no matter how hard you try, this mathematical problem cannot actually be solved (and we can prove it, too)."
These aren't "hard" problems, they're simply questions that don't make sense. Is finding an odd number that is divisible by 2 a "hard problem"? I don't think so, it's just that it turns out that it doesn't make sense to ask the question.
Some of these "hard problems" actually have solutions that demonstrate they aren't solvable, and these solutions are fairly elegant, in which case I'd also say these are not "hard".