This. The statement that you have a right does not give you carte blanche to kill anyone who infringes in the slightest degree.
We are dealing with subjective perception on both sides. Neither the civilian nor the officer are given supreme ruling authority as to what the law does or does not say. The US Supreme Court gets the final say. So it is unsurprising that limitations are placed on both sides that move the decision to the realm of the courts.
Allowing the police to lose in the honest fulfillment of their duties would undermine the entire legal system. You must give them some wiggle room as an ideal as they never have surety as fact that they are covered. Judges are human -- they make mistakes and their decisions can be greatly influenced by moods. If you do not color them slightly towards giving the police the benefit of the doubt, the core functionality of the police is crippled.
Humans are emotional beings. If you do not allow them to proceed in daily life emotionally, they get bitchy.
Setting a rule that makes the civilian restrain his emotional perception once is better than setting one that places the burden on the police of restraining it all the time. The civilian is protected if his emotional perception turns out to be valid, so that doesn't rate anywhere near if the entire police force decides to up and give a middle finger to the legal system. If the police decide to let the system fail because it's too restrictive on them, you can't fix it while maintaining the restrictiveness. You may be able to put a band-aid on it by quadrupling their salaries, but the underlying moodiness will still be there.
Conservatives have a sense of absolute entitlement and always want to be completely unleashed dogs. Sorry, but sometimes the reality of society requires you to place some leash on yourself so as to allow for other people's doggyness.
You are not the center of the universe. The burden is not placed on solely on everyone else to accommodate you. You have to accommodate others as well.
Such is just the way of reality. If you have a problem with it, take it up with your god. Ask him why he didn't actually make you the center of the universe and demand that he change it because, as the proper center of the universe, even your god should revolve around you. Amiright?