The whole spectators being arrested was a comment on the street racing thats been happening here in Atlanta. I agree, people leaving an event and happening to witness a fool wrecking would not have been doing anything illegal.Street racing would require a secondary vehicle. This was just an asshole driving like a dick which are traffic infractions not even on the same level as the crimes you mentioned. This was a coffee and cars meeting which is not illegal by the way. So no the spectators are not committing a crime. Just a driver making a poor choice.
Your youth incident is an illegal stop and it’s not illegal to have tires in a truck. That stuff would not fly now days especially with all the cameras.
Lots and lots of things were different in the late 60s and early 70s.... Including youth attitudes towards the police. Back then my teen age self never would have even thought questioning them would even be an option.