[mpreda]

It seems to me you're projecting our own human nature over all possible intelligent life.

But with a bit of imagination the potential space of intelligent life is much larger than just "displaying human-like agressive traits".

[nathanmurfey]

Sound reasoning when applied to the alien civilizations themselves. However, the dark forest problem (which is what the original commenter I think is talking about) extends beyond the idea that aliens may or may not have agressive traits, if you believe that there are thousands of alien races out there, you only need one to be technologically advanced and decide that humans are too "agressive" to be left alone.

Upate: Other people in the thread have mentioned 3 Body Problem, I would recommend taking a look, it completely changed how I think about this.

[samus]

The loss of not making contact with friendly aliens is probably not very high. Attracting aliens whose presence would have negative impact for us would be catastrophic. The aliens would not even have to be that aggressive - there's plenty of different ways that civilizations can harm each other, even if it might not be intentional.