As far as friendship/protection/leadership goes, an analogy that works for me in describing "the way it should be" is to think of it as a similar balancing act to good parenting. You are the "parent" of a "child" who is ignoring, back-sassing, and doing his own thing. It's time to delineate some boundaries, as a matter of safety.
Horses exercise leadership over one another by moving each other's feet. A strong leader creates "pressure" through body language, escalates that pressure if necessary, and releases the pressure when a lower-tier member of the herd complies. If that lower-tier horse resists or "pressures" back, and the leader submits by moving their feet and "giving ground", then the lower-tier horse gains "points."
Strong leaders in the horse's world are not tyrants -- this is where "friendship," as the horse understands it, enters the picture. As long as the leader's position is not challenged, he/she is content to work with the other members of the herd; swishing flies off of one another, sharing lookout-duty, etc. The leader doesn't go around actively enforcing their position, but goes about life in a relaxed, even passive way until the behavior of a lower-ranking horse necessitates an appropriate response.
Protection comes in when we understand how lower-rung horses percieve superior horses and the herd boss. Because the leader is confident, he/she is the last one to spook in a crisis situation. Each horse is going to look to the horse above him in the hierarchy for cues and updates about current safety and security -- If I'm at the bottom of the pecking order, and the guy three steps up the scale sees something that scares him, I better pay attention, too. If there's something happening that even the Leader isn't confident about, it's really something for me to worry about. So, each horse relies on the ones over him in the hierarchy to tell him something about his own safety. The Leader doesn't have anyone to take those cues from -- he is then responsible for his own survival, as well as that of the rest of the herd, since they are all looking to him. So, the Leader's position is rather stressful.
Why do horses challenge one another (and their humans) for leadership, then? It's a matter of safety. As low guy on the totem pole, I want to be certain that the guys farther up are up to the challenge of telling me when I need to run. The only way to be sure of that, is to see if they can keep me in line. If they can't do that, how can they protect me any better than I can protect myself from the things that go bump in the pasture? Without any other effort or change in tactics/approach, then, by becoming your horse's leader, you are also his protector in his mind.
Becoming a leader that your horse understands is a matter of confidence, attitude, and being able to respond to your horse's responses to you the way a boss mare would. Some horses take a subtle hint; an assertive stance and eye contact can be enough to get the point across. Others are a bit harder to convince, and require their leaders to really demonstrate some competency. Groundwork can be a great way to get the ball rolling and establish a pattern of calm assertiveness in you, and of relaxed, giving submission in your horse. Focus on getting him to move his feet out of your space, and reward the smallest change and the slightest try. Get him moving forward, backward, left and right. Depending on your horse's particular needs, be sure to balance this kind of "sensitizing" training with "desensitizing" to ensure that he isn't reacting out of fear of you or your equipment. As far as rewarding a good response, most horses absolutely love it when pressure is released. They understand release of pressure naturally as a "reward" for good behavior; it isn't something that an association needs to be created to understand. No treats required. For very pushy horses, the last thing I want is to be percieved as a giant walking treat dispenser anyway.
I'd definitely take a lunge whip with me into the field. Personally, I don't much care if there's a rukus about it, as long as it happens well out of my space and I am able to enforce that space when necessary. If you aren't familiar with it, study up and practice "whip etiquette," and how to clearly express "get out of my space" versus "I am approaching you now, do not run." Whip handling can be an art in itself sometimes, lol.
Anyway, there's my 2 cents on the notion of leadership, respect, and how to get it from horses... amazing how tricky it can be to put it all into words in a forum, eh? Hope that's helpful to you, and good luck!