Last I checked swear words don't justify blows to the face. Now lets say you did have good reason to hit him in the face and then you go for the keys per the rest of your plan. Guess what, this has happened before (grabbing the keys) and often the officer gets dragged by the vehicle. Not so simple is it.
Oh and forgot to mention if the guy drives away dragging the officer and the officer shoots because his life is in danger they will still turn around and say the officer put him/herself in danger.
Officers have a job which requires them to place themselves within danger. If someone tells you that there is no duty to step in and protect then they don't know what they are talking about. If one person is beating up another and the officer stands and watches because he doesn't want to place himself in any danger then he gets fired for cowardice. Now there are limits of course, an officer isn't expected to go into a burning building, for example, but yes they are required to go protect someone.
If a cop watched a suspect stab your grandma to death and did nothing are we all just going to sit around and say to ourselves, sucks for grandma since the officer has no duty to protect.?
You are ill-informed and incorrect. In response to your statements:
Officers have a dangerous job but they are not required to protect you. If that was the case then we wouldn't have court cases finding that cowardly police, hiding in the steersman's cab of a subway train, watching a citizen battle a knife wielding killer, saying that, now would we?
http://thelibertarianrepublic.com/nyc-police-duty-protect-hero-video/#axzz3DjCHHZSTAnd to answer your last question, yes, if a cop wants to sit around and watch grandma get stabbed, he can.
I don't mean to be rude, but you really should know a little something about a topic if you are going to comment on it, especially if you are going to make the allegation that others "...don't know what they are talking about.." Calling people out about their perceived ignorance when in fact it's you that are wrong is, well, rude and disrespectful.