I'd feel it would clearly cross the line if the chant singled players out. " Turner" or something.
"F-U Texas" is crass and not very creative, but if you're deeply offended, you could use some pearls to clutch.
That said, if this becomes a bigger deal than one Instagram page and the student section gets reprimanded, they should be creative and show up at the next game early and chant "Welcome, Yale" or "Welcome To Our Home" or something. Put it on YouTube and call it a day. And then Instead of "bullish-t" after a bad call, chant "we humbly disagree"