There is something else to think about. With respect to alien intelligence, those entities that are overly aggressive may not even survive the nuclear era. Think about it. If Kennedy was a little bit more aggressive, and actually launched preemptively, and considering the retaliatory nature of the Russians, it could have been the end for us. We seemed to have survived this era so far. But there will be other era's. For example, the fusion era. Developing other exotic energy based weapons will pose a challange as well.

NOw imagine an alien intelligence that has survived all that. It would seem to me that this intelligence could not be overly aggressive. So I'm really not worrried about the extremely advanced ET's. The one's I worry about are the ones only a few hundred to a couple of thousand years more advanced than us. Those cochroaches could pose a problem!