“Outside of Christ, you (and your spouse) will live with a person who possesses a worldly, anti-Christian worldview.”
My wife is a Buddhist. I am not religious. Neither of us are anti-Christian.
The use of the word anti as in anti-Christ or anti-Christian means "over against, opposite, instead of". Those who are not in Christ are in/into something else. "Instead of Christ" I believe (fill in the blank). Anti-Christian doesn't necessarily mean a person hates Christians or Christ (although many do). It simply means that a person adheres to a belief, someone or something other than Christ - rejecting Christ as Messiah, the Son of God.
The Greek in scripture for anti as in "anti-Christ" means: "473 antí (a preposition) – properly, opposite, corresponding to, off-setting (over-against); (figuratively) "in place of," i.e. what substitutes (serves as an equivalent, what is proportional)." re: https://biblehub.com/greek/473.htm