Lip service and mere geo political realities are two totally different things. The Americans have stated that they are perfectly okay with the Chinese managing the Gwadar port, but in reality are they? Just because the Americans have stated something does not mean that they will stick by it.
The mere fact is, the Western World and Arab World spearheaded by Israel and US will do everything in their power to try and isolate Iran. As long as the Ayatullah is in power and Ahmadinejad chants 'Death to America and Israel', they simply will not accept Iran getting strong economically because that would translate into Iran getting strong militarily. India's trade with the Arab World, West and Israel far eclipses her trade with Iran. So far the port has made very little impact in economic terms, if the port starts getting busy and more money starts to flow in the pocket of the Iranian Regime, you can be damn sure that there is going to be immense pressure from these above mentioned powers to try and rein India's trade with Iran. Already the Americans have been successfull in forcing China and India to reduce their oil imports from Iran, heck India is paying Iran by wheat because she cannot access the International Financial System. You can't have the cake and eat it too, you simply cannot milk both sides, thats how the world of geo politics is. The Arab and the Western World offer a lot more milk than Iran, so its natural India will choose to milk them instead of Iran.