If one can't successfully appeal to someone's sense of morality (perhaps because they have different morals), one can try to appeal to their sense of self interest.
This one, uh, I point-blank refuse to believe. The moral principles about how you can treat other people are so widespread and uniform (made it into the bloody bible, even; the only bit that everybody knows from that MLK speech is about this), that you're gonna have some serious convincing to do, before I believe that people "have different morals". It seems more believable that people have just the same morals they always did, but are applying them very selectively without proper justification (as it always is with prejudice).
And in getting them to apply morality in a more uniform matter, sometimes it's easier to address morality by way of self-interest than morality directly. Getting someone to acknowledge than a random Iranian being allowed in the country will not cause buildings to falls is a good thing, and whether it's achieved by appealing to their morality or their self-interest it's still a good thing.
People's answers to things like the trolly problem says we do have different morals and the way you frame a question has a lot to do with what we think is moral.
What are the proper justifications for treating other people as less than people?
Believe what you want, different people believe in some fundamentally different things. Go hang out on Breitbart, and see if you still feel the way you do.