But I agree I don’t think that people cannot handle it. Science fiction has acclimated people to this.
Not just science fiction. It is hard to find an historical example of an earlier civilisation that did not believe in some form of life external to earth. Generally these beliefs came in the form of a God or some form of creator being – but such beliefs are still consistent with there being an external living entity. The exception to these ancient beliefs is the totally irrational Darwinian concept that there was no creator – and that life on earth popped into existence by accident.
Having said that however – I expect, if it becomes undeniable that we are being visited by aliens, this is likely to pose some difficulties for the millions of people who have conceived of a God in a different form. I guess that will be up to the various religions as to whether their beliefs can accommodate alien visitors.