This is a valid point, and I'd take it a step further. Not only are we not well suited to speculate on the nature of life "at large", we're even less suited to speculate about the nature of intelligent life (whatever that even means).

On the other hand, should we encounter sentient life, it certainly is not difficult to imagine hostility or callous indifference -- from either party. Particularly if said encounter is not on our terms.

And as profoundly exciting as the prospect of meeting alien life would be, I'd much rather it occur sometime after we've grown up a bit, ourselves.