Sheriff Teasel illegally detained Rambo twice without probable cause. Teasel went on to failing to read him his Miranda rights which again lead to an illegal search of his person. A judge may find that an officer searched him for his own safety, but the arrest was baseless.
Walking is not vagrancy. An "American Flag" on your enlisted army jacket is not a decoration. No different than the American Flag on Sheriff Teasel's police jacket.
Attitude is conjecture. I was a fact, that John asked: "Why are you pushing me?", after asking about a place to eat. Teasel tells him about a place 30 miles down the road.
The sheriff had no grounds to arrest John Rambo. It was a clear violation of his Constitutional Rights.
How could you possible say the deputies actions were legal? After John takes off his shirt and turns around as commanded, he is struck with force in the small of the back by a police baton by Deputy Galt for no reason at all. Complete crime right there.
John Rambo then begins to defend himself after the brutal hose down and restraint put upon him as they bring a blade to his throat saying "I don't want you to cut your own throat." PTSD kicks in and survival mode takes over since no one seemed to follow any law except doing whatever they wanted to Rambo.
Later on in the film, the other deputies reveal to the Sheriff that Galt had been abusing Rambo. So there is the brutality charge.
Furthermore, after Galt falls from the chopper and Rambo puts his hands up to surrender, the police open fire upon him. Now the police could be charged with attempted murder, assault with a deadly weapon.
Despite all of this, Rambo did not kill anyone, Galt was at fault in the helicopter and at best Rambo was acting in self-defense as he is on a cliff, no gun, and being fired upon from a helicopter.
Perhaps you should watch the movie again. May want to check out the Constitution as well as the Bill of Rights. Because, you know, cornering a suspect in a cave and firing a rocket launcher into the cave may be considered excessive force yet again.