Xenos = foreigner, Phobia = fear or dread.
Treating the hard working and generally cool people that come to the US as being in the same boat as all us humans but bringing interestingly different solutions for how to conduct our affairs is not cultural relativism, it's being realistic and open to the goodness of creation, to seeing each person as bearing the image of God in my own religion's terms.
Seeing the current crop of immigrants as being lazy, criminal, disease ridden or a source of decline in the quality of life for the people in the US is xenophobia, it is irrational and not-truth based.
Prefer whatever you prefer, that's the bed rock of a free society, and welcome the people who value freedom and hard work so much they have fought to join your country. Or you condemn your country to a period of diminishment, superstition and other forms of backwardness.
> The countries that most immigrants come from treat that principle as axiomatic.
Haven't spent much time overseas? I have, and I don't find this to be the case - most (tho not all) likes their family ways more than others, and many many places have built cultures built on the idea of syncretism, of one culture out of many. In a way the very genius of India is that it's made of hundreds of cultures work together as a pleasing whole greater than any part. And of course "E pluribus Unum" has proven to be a potent idea in the history of the last few centuries.
The very stereotype of the sophisticated Muslim who quotes Maimonides and Jesus as readily as the Prophet, and is well versed in scientific arts and is great in his or her career is a stereotype based on a millenium of encouraging arts and sciences and great cities built on many cultures working together.
Denying the plain reality of immigration because of fear of some made up "cultural relativism" is irrational xenophobia, in my book. No one is trying to shut down your church dinners and NFL games.