What about if SETI@home had been programmed by aliens, so we all thought we were looking for them, but the code would never find them? :)
Obviously the easiest way to provoke thought within the skeptic is to ask, “If it is within the realm of possibilities for the human race to invent a driver allowing interstellar travel, why shouldn’t an extraterrestrial race also be capable of it?”
I would assume someone would counter with the fact that extraterrestrial life hasn’t been discovered. A question to often revisited. For all we know extraterrestrial life surrounds their inhabited planets with strict ingress and egress policies.
If you think about how some scientists responded to speculation about Oumuamua you can see how they were nervous about speculation that could be sensationalized.