If it weren't for the context, I don't think it would matter to me personally. As long as it was a once in a blue moon thing. A way of pledging allegiance yet contributing their own voice to it.
That said, the context is completely wrong here. Not to mention the lyrics have been changed to sound like some communist workers' party march. Then we have these knuckleheads flying the Mexican flag, being here illegally, demanding rights, sucking the taxpayers and our hospitals dry, and they have the audacity to sing OUR national anthem in SPANISH!
I can't respect that in the slightest.
Even if you don't speak the language, you can learn to fumble your way through the English, making a best effort. That would demonstration an aspiration to solidarity with American culture.
Singing it in Spanish in this militant "context" (even if the correct words were used) is a declaration of a new type of citizenship -- Mexican/American...not a transitory hyphenation but a dual-citizenship. It makes me sick.