Yes, as intrigued as I am at the possibility of contact from space aliens, I think he’s right. If intelligent beings do exist elsewhere; I’m nowhere near his degree of probability on that; we don’t know what they might do. For all we know, they could kill us, enslave us or harm us in some way. Yes, they might also help us; they could share their technology and share their knowledge about the universe; but that’s a chance I don’t think we should take. As far as I’m concerned, we should try to go as unnoticed as we can.