At this point, we're veering far off the fundamental subject. If you would, please answer the questions given an assumed scenario. I know that we don't have the video and the OP might have missed some or ALL of the details, but let's just assume for the moment that:
1) Perp was merely seen emerging from the parked cars's window.
2) No crack pipe was seen at the time. No other paraphenalia either.
3) None of the cops know anyone or any of the cars/houses on the scene.
4) Subject walks away from the car.
5) Subject continues to walk when the cops ask for him to stop.
6) The officers both suspect drug activity, but no physical evidence was actually seen.
The Question: Is it right and just for the officers at this point, knowing only the information above, to forcibly detain the subject?
With regards to #1, if the area is known for high crime or drug activity and the individual was exhibiting specific behavior (e.g. stopping by a car window in a neighborhood where that is the common method of drug delivery), that is more than enough to justify a Terry stop of the suspect.
This would, of course, allow for a pat down to look for weapons or contraband. As to whether the suspect can be forcibly detained, officers are permitted to use reasonable force to detain a suspect who can be lawfully detained.
Police don't HAVE to see crack pipe. If they did, that's probable cause to arrest and they can do that right on the spot. But a combination of suspicious behavior consistent with a crime in an area known for that crime will fly by a judge as being reasonable articulable suspicion to conduct a Terry stop.
Edit: With regards to number 5, if an officer actually says to you, "Stop," you can bet your sweet ass that's not a request. Even if you *think* you're doing nothing wrong, stop, turn around and ask if you're being detained.
In the scenario you've given, LEO's would be well within their duties to act.