I cannot say with conviction that aliens exist, but I'm pretty certain they exist because it is, in my opinion, a statistical improbability that only one planet out of a countless amount has life on it.

As regards to aliens being extremely advanced and benign is a strange and unjustified stereotype, for all we know, they could be as technologically as advanced and malicious as us humans. In fact, they could be more primitive, thus explaining how we have not had any contact with them (although we may have had contact with them for all I know).