I tend to agree with that - although with all the stories going around, maybe some stuff has gotten out, but has just been completely ridiculed so it won't be believed.
As far as whether they are here or not, I liked the analogy of an ant colony next to the super highway. I don't think there should be any assumption that aliens would be even remotely understandable or even detectable by us.
Speaking for myself, I'm always interested in the possibility, my mind remains open despite the pollution that overwhelms the subject from the tricksters and the occult. This is probably because I personally witnessed an unexplained "sighting" once before, but it wasn't something that was completely impossible by man, nor have I seen evidence of anything yet that wasn't possible by man.
I don't think there should be any assumption that aliens would be even remotely understandable or even detectable by us.
All assumptions have to be that they don't exist, since there's no substantiative proof to the contrary. I'm open to the possibility, but I do not assume anything exists without significant reason to.