As for Giuliani, he has indeed stated how he would deal with Iran. In the September/October edition of Foreign Affairs, he wrote:
"The next U.S. president should take inspiration from Ronald Reagan's actions during his summit with Soviet leader Mikhail Gorbachev in Reykjavík in 1986: he was open to the possibility of negotiations but ready to walk away if talking went nowhere. The lesson is never talk for the sake of talking and never accept a bad deal for the sake of making a deal. Those with whom we negotiate -- whether ally or adversary -- must know that America has other options. The theocrats ruling Iran need to understand that we can wield the stick as well as the carrot, by undermining popular support for their regime, damaging the Iranian economy, weakening Iran's military, and, should all else fail, destroying its nuclear infrastructure."
There are limits to how we can deal with Iran due to the necessity of keeping the Saudi royal family in power, yet Giuliani has shown that he will take a more direct approach. Hillary's approach is far to naive and rests on Iran simply agreeing to play nice, which goes against the very nature of how nation states act. Hillary is the one that is clueless, not Giuliani.
Obama could be described as naive, but it wouldn’t matter a bit. The President is not a one man band. We can only be as tough as our foreign policy establishment lets us be, as GWB has learned to his cost. Only a powerfully counter-cultural President, like RR, could deflect our policy more than a fraction and neither Giuliani nor Clinton is counter-cultural in the least.
In an election between Rudy and Hillary I have no dog in the fight. I see no grounds for choice and consequently I won’t make one. The suggestion that our foreign policy will be more muscular with Rudy at the helm is utterly unsupported by the evidence so it does nothing to sway me in Rudy’s direction.
Notice that, in the passage you cite, Rudy doesn’t call for undermining the Iranian regime, only for making it clear the we can if we get really mad. After Iran has waged war against us for 28 years, that is pretty weak beer. For every one of those 28 years gasbag politicians have been saying that Iran has to understand that we can be a dangerous enemy, and yet the Mullahs are still in place unscathed. The Mullahs have long since stopped attaching any meaning to the empty words and so have I.
If the Republican Party is foolish enough to nominate Rudy I will at least have the satisfaction of watching somebody I despise lose. Cold comfort but better than nothing.