For us, that's reprehensible and an absolutely vile and disgusting thing to say. But for most of the world, the F word just isn't that big a deal.
If we're having a fantasy draft and I take a specific player, it's not uncommon for a buddy to say "Oh f*** you krindorr, I was going to grab him". It doesn't mean he hates me or is even that upset. It's said good-naturedly, and knowing how he means it, I can't even take real offense.
The chants are just differences in how something is perceived, more about differences in how language is perceived, rather than about how incredibly vile fanbases treat BYU. Because to them, saying that just isn't a big deal. Just a convenient rhyme with appropriate syllable breakdown.