I really enjoy this question. I feel like it actually touches upon whether or not you're an optimist, pessimist or realist in your ideals pertaining to strangers.
For the most part I agree with what most of the other posters have already stated. People deserve a basic respect, "common courtesy", all other forms of respect can be lost or gained through your words and actions.
However, it's not black a while in Respect either. While you can respect a person's actions you may not respect the person. Or Vice Versa. Take for instance a young teenager that steals to feed a younger sibling because there are no parents to provide. Although the actions taken are wrong, you have to respect the kid for trying to provide for the younger sibling.
Also