Wouldn’t a True Christian Refuse to Leave People Behind in Hell?

Questions about whether the fast rate at which Christianity spread is evidence it’s true, whether a true, loving Christian would refuse to leave people behind in Hell by accepting Heaven, and challenging someone who favors religions that pre-date Christianity because they’re older.

• If the fast rate at which Christianity spread is evidence it’s true, how do I square that with the fact that there will be as many Muslims as there are Christians in 2050?
• Would not a true, loving Christian say that if anyone has to experience eternal torment, then they have to as well? Is it possible God is testing whether some of us will accept Heaven and leave others behind?
• How would you go about challenging a person who favors religions that pre-date Judaism and Christianity because they’re older?