As I noted in my other comment, this argument just makes a more precise version of the original mistake. You could just as well say that:

no matter how much you give to CARE about the election, your vote will never make a serious dent in the outcome. There are just too many other voters. Therefore, you shouldn't bother voting against the lizards who just agreed to reduce permitted human lifespans to 34 years.

Incidentally, Landsburg advises against voting, for exactly the same reason, so it's worth pointing out that if you don't accept that argument there, you shouldn't accept it here, either.

I should also add that this doesn't meant the argument is wrong; if you agree with not-voting and not-charity-splitting, fine. But you should make it with knowledge of the parallel.