Irreligious people often/usually don't bother to understand religious people. Dismissing ideas and people tends to do that. Spielberg claims that he returned to his roots in Judaism in the 1990s, but he has strayed really far from his Orthodox upbringing, and I wonder whether his return was more in the realm of deeper cultural Judaism - meticulously observing the customs, but not really diving into the meaning of God's LORDship.
It's interesting Spielberg singled out Christians, not including Jews, Muslims and other non-pantheist theistic religions. Sounds like Spielberg harbors particular animus toward Christians. His family lost nearly 2 dozen members to the Holocaust, but he should realize that the Holocaust was not a "Christian Thing" and that most American who fought against the Nazis were Christians, many of them of Germanic family heritage and German-speaking (e.g. my Uncle Erwin, whose first language was German; the US Army had enough German translators that his mechanical skills were more needed).
Comments about the movie I've seen/heard have been that it's boring and stuck in the "Close Encounters ..." 1970s. How object thoes people are,

.
Larry Norman had a song in the 1970s that in part speaks to the possibility of "life on other planets",
https://www.youtube.com/watch?v=gjd265vNIlQ&list=RDgjd265vNIlQ&start_radio=1 . Two of the books in C. S Lewis's "Space Trilogy" speak of life on Mars and Venus, which while fiction, demonstrate that the possibility of extraterrestrial life was/is not particularly troubling to Christians. If Spielberg thinks Christians would find the idea of extraterrestrial life troubling, its an artifact of his lack of understanding theologically conservative Christians.