That IS why Christ came, made a sacrifice of Himself AND instituted His Church. Having friends over for dinner no matter what their religion is a far cry from helping them prepare for their eternal end.
No one is suggesting that cruelty is the answer - all I’m saying is that telling our neighbor that everything is fine; that his pagan, atheist, or heretical beliefs are just as salvific as Catholicism is not charitable in the slightest. We should point out to our neighbor that he is running to the eternal flames; we should embrace him for the sake of his soul, not clap him on the back as if his wayward beliefs pose no threat to him.
Hear what the Bible teaches:
"They that say to the wicked man: Thou art just: shall be cursed by the people, and the tribes shall abhor him. They that rebuke him, shall be praised: and a blessing shall come upon them." -Prov. xxiv. 24, 25.
"Them that sin reprove before all: that the rest also may have fear." -1 Tim. v. 20.
And there are many more such passsages. It is our job to judge what actions are morally wrong and right so that we may ourselves engage in right actions. And when our neighbor falls by the wayside, do you imagine that his actions will have no effect on the just, or his own soul? We can not say who is in Heaven or Hell, but we are expected to determine the just cause from the wicked.