See, "Can Iran be stopped? The West should intervene in Syria for many reasons. One is to stem the rise of Persian power":
The growing risk of a nuclear Iran is one reason why the West should intervene decisively in Syria not just by arming the rebels, but also by establishing a no-fly zone. That would deprive Mr Assad of his most effective weapon—bombs dropped from planes—and allow the rebels to establish military bases inside Syria. This newspaper has argued many times for doing so on humanitarian grounds; but Iran’s growing clout is another reason to intervene, for it is not in the West’s interest that a state that sponsors terrorism and rejects Israel’s right to exist should become the regional hegemon.RTWT.
The West still has the economic and military clout to influence events in the region, and an interest in doing so. When Persian power is on the rise, it is not the time to back away from the Middle East.