The Killing Star by Charles R. Pellegrino makes a very compelling argument that if aliens do exist, we are probably royally screwed.

Can we honestly say that evaluated from the outside as a species, we are not pretty close to a threatening, violent, virulent plague? I think our only hope is that the ET's are both extremely benevolent and too powerful to consider us anything approaching a credible threat. But the scenario outlined in the book about relativistic kinetic kill weapons being a great equaliser speaks to a dark future in the event that we ever attain the necessary technology to be such a threat.

Hopefully by then our historical track record won't look quite so psychotic.