Paul's objection is flawed because he assumes that a "good" deal would require Iran to fulfill all of its obligations before it gained anything from the agreement. If the deal had been structured this way, there probably wouldn't have been an agreement. More to the point, sanctions relief is what the U.S. and the other members of the P5+1 are expected to offer as their part of the bargain. If these governments didn't offer any sanctions relief at the start, they would be failing to comply with their commitments. In short, Paul is opposed to the deal because it includes a compromise that was probably necessary in order to secure an agreement that achieves a much more important goal. That's no reason to oppose the result of a successful negotiation, and it suggests that Paul wants to continue his vain efforts to placate his party's hard-liners.