I would be open to an argument that goes like this: "We can't afford to fund exploration of space with tax dollars when our earthly concerns cannot be paid for without debt." That is, I WOULD be open to such an argument if the same logic was applied across the board...
"We cannot afford to fund the United nations when our national concerns cannot be paid for without debt."
"We cannot afford to fund the National Endowment for the "Arts" when our national concerns cannot be paid for without debt."
"We cannot afford to fund ACORN when our national concerns cannot be paid for without debt."
To be clear, I am not claiming that NASA funding should be cut or not. Only that justification for the cut follows no logic whatsoever.