Interestingly, you have the same amount of evidence for E.T.
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That is an inaccurate comparison. More accurate would be to compare the people who not only believe ET might be out there but to compare the people who believe ET is out there and they are the Grays and those Lizard people (don't remember their names) and a host of others. There are elobrate descriptions of what these aliens are like, how they have directly influenced earth, that they were responsible for seeding life on earth etc.
I think most of us, religious or not, would agree that the small set of people who believe such things have an irrational belief. Such a specific and detailed belief system without even thin shards of evidence to support it is a bit on the crazy side even though many claim to have had a personal experience such as an abduction.
Now on the other hand you have a bunch of people that generally accept scientific view points who advocate that there is a good chance life exists out there. They have no proof. They have compelling reasons to turn on the spot lights and look for it. They almost never believe in the elaborate descriptions of the Grays and other popular aliens. They do not claim to know for certain aliens are out there (or at least the few in this group who do are the exception).
So yes, if you are talking about the first group I agree, they can be compared to religion in the way you did. As for the second type, rather than being a specific belief set in aliens without evidence, it is a mind set about the best way to proceed in our search for evidence. And if we never find it, look at how much we are learning about the Universe in the process anyway.