It's a little bit different when the "colonizers" have also themselves been displaced over and over and over throughout history, been targeted with pogrom and genocide.

One has a special obligation in such cases to clarify that, no, this is not more of the same.

Especially when in a context where others are saying, "Yes, more of the same!"

I don't think it's unreasonable to ask Americans to jettison "from sea to shining sea" if it continues to bring pain and fear upon people. If the day is so long past that the only people bothered have to willfully be instructed to be bothered, then one could declare the phrase redeemed and just move on.

But, anyway, if the Luther College people have managed only to use this phrase on signs and left out all the other ones that should legitimately cause fear in Jewish students (e.g. "globalize the intifada", "by any means necessary", "glory to the martyrs", "we are all Hamas", etc.--I couldn't find good photographs of the protest so I wasn't able to see which signs were present), perhaps the peaceful and humanitarian intent can be conveyed with education, as you have done.

Pragmatically, though, why wouldn't students choose language that was as supportive as possible to the plight of Palestinians without running the risk of sounding like they endorse terror, and a one-state solution with Jews ethnically cleansed until they are powerless? Netanyahu's government claims that the IDF has to defeat Hamas militarily now because the only alternative is to be subjected to terror and ethnic cleansing of Jews. Why would one, upon seeing the horrors visited upon Palestinians, not speak as clearly as possible against this, rather than use language that plays into that argument?