Wouldn't it make sense that if a CITIZEN doesn't want his tax money going to something he should be allowed to specify that? So, if I am against a war, or a social program, or abortions, why shouldn't I be allowed to direct that MY tax dollars NOT support something I am morally opposed to. I'm not saying out of paying "taxes", I am saying direct that my portion of the taxes not be used for something I morally oppose, and will not "use".
If you can't do that then Democracy just becomes a tool of Socialism/Communism. Maybe it would have been too difficult to do in the past, but with today's computers and networks, I'd bet the implementation cost wouldn't be very high -- although it would certainly be expensive for the collectivists, as THEIR taxes would need to soar dramatically, to fund their redistribution schemes.