Do you beleive in Aliens? is kind of a loaded question. Suggests all the crazies.There's the ancient civilizations crowd, the alien abduction crowd, the little green men crowd, the "We're God's greatest (only) creation" crowd.
We'd be crazy to think we're a statistical outlier - the only possible combination of events to support life. Once you consider we're probably closer to the mean, the amount of other life and intelligent life in just our galaxy - not to mention the universe - is huge. Arrogance is thinking we're the most advanced and just because we're not capable of travel over long distances or long times, no-one is capable.
The further we reach outside of our own neighborhood, the more attention we're going to attract from others. They know we're dangerous. At this point it's still just a matter of monitoring and containment for them.