Surely if there are intelligent creatures visiting earth then their capability and thirst for war is not so different from our own. Makes me think that our government is involved on a cover up on a number of levels.
1). Aliens have visited and they are indeed in contact with them, in fact much policy on Earth is directed by them, otherwise they will attack. The current economic crisis is directed by them. They have instructed bankers to pump the economy full of cash to bring us into such a state of submission and crisis that we will have no choice to surrender to them when they do finally arrive.
2) Our government has explored space far more than they are letting on. We have actively made contact with aliens even before man allegedly landed on the moon. In fact Neil Armstrong is said to have mentioned other classified missions in space which received no coverage. My belief is that they were well before 1969 and far wider ranging than the moon. That agreements were signed with aliens to prevent knowledge of them becoming widespread so as to maintain the current world order. The knowledge of alien lifeforms is of course a threat to whoever is in power.