Curiously you still have not answered whether people that claim to have seen alien visitations can be interpreted as validation for the probability of alien visitations.
I'll just jump in with an answer - no, it cannot. Not in any scientific sense anyway, which is all that matters to us. Who cares what is and is not admissible in a court...
If increasing the number of planets increases the probability of life on other planets, does not increasing the numbers of people who have had similar experiences increase the probability of what they are claiming as true?
I trust you are asking this rhetorically with the obvious negative connotation? If not, then I'm afraid I will have to call for the yellow van...