While it was certainly very wrong for those people to walk out, I can understand the feeling of those who believe that in the United States sermons should be in English unless the parish is specifically spanish speaking. It is a big deal for the English speaking members of the congregation to have to listen to a sermon in a foreign tongue once a month. It does feel like displacement.
It's mistaken to call it racism. If they were racists why would they go to mass with non-whites? Objecting to the language is not racism.