It's wonderful that you are thinking so deeply about this and asking questions Zab. I commend you for that. Some people never think about this, and some people just don't want to because they don't care.
Horses never do something for no reason at all. Nothing means nothing, everything means something. If a horse spooks, he's not doing it to get out of work. He's doing it because he's scared IN EVERY CASE. Spooking is a fear response.
Any "negative" feedback we get from our horse (be it biting, kicking, rearing, bolting, herd sourness, not going forward, etc) shows us several things: 1) how our relationship with the horse isn't as strong as we might have thought, 2) that our foundation needs work (but this is a gift!), 3) that we have actually not been acting like our horse's perfect partner or leader.
Lets look at the unconfident horse first, the one who is herd sour. The horse views the barn/herd as the place of SAFETY. Horses want 4 things, safety, comfort, play, then food. If the horse doesn't feel safe, he isn't going to be comfortable and he certainly won't be worrying about playing and food. So it's our job to prove to the horse that WE are the place of safety, that he can trust us no matter what. But how do you do that? You DON'T do it by working the crap out of them when they act herd sour. That is just force IMO. The horse is only acting like a perfect horse (a prey animal) so he should not be punished for acting like what he is. You have to understand his mind set and really put yourself in his shoes. He's unconfident and scared to leave, so you work with approach and retreat of his thresholds and never ever push him over those thresholds. If you take the time it takes, your horse will start to view you as a worthy leader because you understand WHY he is acting herd sour and he will feel more confident in you because you aren't pushing him over his thresholds. A good leader isn't someone who forces and makes and has a predatory mind set.
Now lets look at the horse who is confident, lazy and sometimes argumentative. This horse is not scared. He isn't looking for a leader. He probably thinks people are useless and could care less about them. IMO this is the more difficult horse to work with because this is a matter of getting the horse to WANT to be with you, to see you as someone worth "talking" to and playing with, and more than that, to WANT to put his heart into things for us. So how do you do that with a horse who doesn't care about people? Undemanding time is the first thing. Don't always work this horse, take him out to graze, spend time scratching his itchy spots, get to know him. People often think that just allowing your horse to graze isn't DOING something in the sense of training.....but it IS doing something, it's making your relationship and rapport with the horse stronger. If you always want something from your horse (specifically this horse) and never give anything back, it won't take long for him to get a bad attitude about you. You just take and take and take and never give anything back in return. And people wonder why some horses are hard to catch, hmmmm. Anyway, the next thing to do with this kind of horse is give him MOTIVATION, INCENTIVE and a REASON for doing something. If you just go around in circles in an arena, that is BORING to this kind of horse. This kind of horse needs VARIETY, not so much consistancy. Motivation and incentive comes in the form of food, sctratches and rest. Using food as a motivator IS NOT BRIBING. There is a HUGE difference between bribing a horse to do something and using food strategically to get the horse motivated. These horses don't want to go forward because they see no point in it, and if the rider treis to force the body (in the form of whips, spurs, smacking, kicking, etc) the horse will shut down even more, put less effort into things and in some cases just stop and refuse to move altogether. I've seen some horses lay down on their riders. You CAN NOT force the body and get results. You MUST get into his mind and motivate him, otherwise the rider will be working harder than the horse, or the rider will just keep using spurs and whips and forcing the horse. Riding shouldn't be that hard! lol. If the horse won't go forward it's because the rider hasn't put enough emphasis on this horse's needs to feel a REASON for doing something. Point-to-point exercises using grazing spots is a wonderful way to get a horse more forward and positive in their attitude. Trail riding, riding on a loose rein, Freestyle riding (working toward TRUE bridleless riding), variety, straight lines vs. circles.....all these things can help a "lazy" horse (who isn't truly lazy, he's just unmotivated) become more forward and positive and to WANT to do things for the rider.
Here is a list (a long list lol) of what I think a true leader is for the horse, someone who is/has/gives/puts emphasis on:
safety, confidence, having a plan, knowledge, security, clear, fun, incentive, consistant, direction, fearless, motivated, resourceful, imaginative, focused, mentally athletic, solutionary, persistant, empowering, apologetic, provocative, brave, courageous, predictably unpredictable, predictable, caring, guidance, understanding, dependable, empathetic, calm, adaptable, flexible, patient, trusting, respecting, goal oriented (this can also be a bad thing), and supportive.