The search for extraterrestrial life is analogous to native Americans back in 1400's trying to contact Europe. Could anything have been worse for the native Americans than the arrival of Europeans?
So I buy a mouse to feed my snake. Could not alien life collect humans to feed their pets? Impossible? I don't think so. Assuming we are the pinnacle of intelligent life is a huge assumption. We are no different than those native Americans back in 1400. They had their technology; the invaders/explorers had better.
The bottom line is that there's always someone with better technology than you've got. If beings with better technology arrive here seeking our resources or us - look out.
Hollywood moving like Independence Day and Mars Attacks that give aliens an obvious and mortal vulnerability aren't realistic. More likely, it'd be like it was in the 1400's; a small ship lands here with a few aliens with better weapons, and they take whatever they want.
I'm not saying we shouldn't search for extraterrestrial life, but we should consider all possibilities.