That is disasterous. That logic is why Chaimberlain allowed Hitler to get more and more and more power. ("Surely they'll agree to peace if we just let them have Poland.")
It is also why my generation (I'm 27) will eventually have to fight a nuclear war that pits Iran against Israel and possibly the US.
That war will potentially kill millions. And whose fault will it be? Obama's and Bush's. They will (if history is just and we don't change course) go down in history as potentially making mistakes that killed millions, just as Stalin and Hitler did.
Or we could insist now (or, ideally, a few years ago) that Iran not develop nuclear weapons capability, if necessary fighting a minor tactical war to stop them.
(There is NO reason to have Vietnam IV, where Afghanistan and Iraq are Vietnam II and III. Except of course socialism for defense contractors and altruism as we throw away trillions "re-building" the latter two countries.)