Ah, the "studies" some people use to justify inaction always kind of amuse me. According to the Oxford Research Group, attacking Iran might make them build nukes. They assume Iran is 5 years from nukes, but say an attack would likely speed the program up. Never mind the UN orders to stop. Iran ignores those, but we shouldn't try to stop their program by force, since that will make them mad enough to speed up nukes.
If your child ignores your demands, you punish the child, right? (I may be making an incorrect assumption on this, since I've seen situations in which this is blatantly not true.) Do you avoid punishing the child because they are going to get mad at you and misbehave more? It very well could happen, but you aren't going to just give up because of that. You just have to punish them until they learn to behave.
If we attack Iran, they may speed up their nuke program (of course, our attacks would likely be targeting their nuclear facilities), but continued military pressure would undoubtedly make them back down. Their leader's crazy, not completely stupid. Letting them finish their 5-year nuke program first makes them far more dangerous. If we want to stop them, we need to do so now, while their retaliation is trying to hurry their nukes.
The really important thing to note here is that the study is "written by a noted atomic scientist and peace campaigner," which isn't really what I look for in political analysis, anyway.