A Coast Guard member's job is to obey orders of the CO, not to delve into philosophy.
Drug smugglers are citizens too. Is it the CGs job to serve them also?
There is no duty to obey unlawful orders, which assigns them just a bit more responsibility than your putative law-enforcement automatons. There is some debate over whether such orders should be unlawful, but I merely suggest that if the Coast Guard abuses its current ability to execute warrantless searches, it will find that power no longer available to it. In the end, the Coast Guard answers to the people, like any other public servants.
Drug smugglers are citizens too. Is it the CGs job to serve them also?
Laws are created for all the people, and are intended to apply equally to all the people, not merely the ones you happen to like. In any case, last I checked, the land-based law enforcement agencies of the country were able to enforce the laws and abide by the Fourth Amendment's requirements for warrants. Surely you're not suggesting that the CG, with its vast resources, is of such a lesser caliber that they are incapable of doing what my county sheriff does every day, right?