there is none if they were here, the democrats would tax them and curry their votes..
The advanced aliens are so backward they have to come down to treetop level to examine us; while we can surveil the entire planet from satellites in space (and even see the indentations in a golf ball).
When they kidnap someone, it is never a leader; just a nobody.
And they are always assumed to be benevolent messianic figures who are here to help us. There is no reason they could not be savage carnivores looking for lunch.
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That may be strong evidence that they ARE here...