The only reason he proposed that was to show that OBAMA's requested spending could be made up with domestic cuts. It was a symbolic gesture as he was the only vote.

Here's what actually happened. Marco Rubio (not President Obama) proposed an amendment to increase military spending which didn't pay for that spending increase with revenue increases or spending decreases elsewhere. Rand Paul saw the opportunity to propose a bill which was budget neutral to use as a political stunt to embarrass Rubio. That's what happened. It was still a proposal to increase military spending, and it legitimized Rubio's goal to increase military spending, while attacking Rubio for being unable to do the basic arithmetic to make the spending increase budget neutral. That's the problem. You have to look at the bigger picture, in which Rand Paul proposed an amendment to increase military spending during primary season to attack Rubio and make Rubio not only seem weak on fiscal conservatism, but also on defense, and he did it by making himself look like a hawk.