Did you see that in the video? What the video shows is that the guard took the sign and was walking away with it. Unless you have video showing the guard had a right to steal the sign, then he would not have a lawful defense.
Maybe the guard was having an affair with the Mexican's wife?
Maybe the Mexican was just trying to hug the guard because he liked him so much?
Maybe....
Maybe....
Maybe....
Man have you lost it! Go to new york and help the poor mexican.