"Love your fellow as yourself". Since what has been written and taught is to love "your fellow", and not "the people of your nation", we understand "fellow" to include all types of people. It is like saying: Be vigilant from vengeance or from bearing a grudge against the people of your nation, because 'love your fellow', whoever he or she is, is an essential principle.
Indeed, we learn this from what follows later in the text, "The stranger who resides with you shall be to you as one of your citizens; you shall love him as yourself, for you were strangers in the land of Egypt." Should you think that this refers only to a convert who has undertaken to follow all the commandments, what is "who resides with you" meant to teach? A convert would be considered like an Israelite in any place. It teaches that the stranger in question is someone who shares no national affiliation with you, and is only residing with you.