I need your help with a Christian in the church I am leading who has started struggling with some thoughts about how aliens have been visiting us for a long time and controlling everything on the earth from the beginning. There are a lot of movies on youtube talking about that with a lot of evidence about all the mysterious things that happened during history that could only be explained by aliens.
My opinion about a fellow Christian who believes in aliens is that this is a totally irrational belief. It is similar to those who are susceptible to conspiracy theories. It is a sign of a person who is poor in critical thinking and is probably fairly gullible. No intelligent, rationally thinking person would ever believe in this sort of utter nonsense. For this reason, no logical argument with this brother will be helpful. I doubt that you will be able to provide evidence which will stop his irrational, evidence-free belief. I have known a few Christians who believed in this kind of stuff. In most cases, the person had some psychological/emotional problems which were the basis for such irrational beliefs. As one of my favorite authors, Jonathan Swirt said it, “You cannot reason someone out of something they were not reasoned into in the first place.”
My suggestion is that you gently tell this brother that his belief is not supported by biblical teaching and that it is not based on any actual physical evidence at all. No scientist and no well-educated person believes in such pseudoscientific things. You should suggest to him that although you think this belief is not rational, as long as he does not spread his irrational beliefs around the church it is not going to be a major issue, but strongly encourage him that he should keep such beliefs to himself. If he has a good heart, he will accept your advice.