Hmm, I'm sure this will spark a debate.
For lazy, mellow horses that don't respect my leg, I will use spurs. Not to "harpoon" them, but to nudge or lightly bump them. It's uncomfortable enough they don't want to lean into the pressure and after they "lighten up" I always go back to using my calf instead of the spur. The spur is just a back up cue. And I don't just jab them in the side. I roll the rowel up their side, it more or less tickles them and that is what makes them get off the pressure. If someone tickles your ribs, it doesn't hurt but you instinctively move your ribs away from it. Then if you see the "tickle fingers" coming at you again, you generally move before they get there, right?
So the spurs, if you give a fair cue before hand, and need to use them, make them mindful of the "tickle fingers" coming and move away, and you dont' have to keep using the spur everytime. It works very well for me and my horses don't sour up to spurs or wring their tails.