"Is anyone here questioning the Mexicans' right to wave their flag? (Didn't think so). "
To the contrary--a hell of a lot of people here were saying things like "get the hell out, if you want to wave that flag." So, you're wrong right out of the box!
And I'd say the same thing to people who wanted to wave the Nazi flag, but that doesn't mean I think they don't have the right to wave them. "Not having the right" means that the activity in question is illegal, and no one here is questioning the legality of Mexicans waving their flag. (Illegal aliens are, by definition, acting illegally just being here, but that's a topic for another discussion).
Again, criticizing their decision to wave their flag or even telling them to "get the hell out of the country" does not equate with the belief that they're not perfectly within their right to wave whatever flag they want.