My personal opinion on spurs is that they should be used to make your cues LIGHTER. Not force the horse to pay attention or make your heels more harsh.
Spurs should be used to make your cues invisible to the outside onlooker. That you can touch your horse so lightly with them, yet your horse responds and knows exactly what you want. Think about it -- your horse can feel a fly land on its skin. Think of how reponsive they can be to the same amount of "fly pressure" with a small touch of your spur. LIGHTER!!!
I don't know the background on your whole story here, but my opinion would be to get your horse to listen to you the way you are. Because what if he starts to just ignore your spurs too, down the road? Then what will you do? I say that you fix the root of the problem, and that's his lack of attention or lack of respect or whatever the problem is. He should listen to you no matter what you ask, no questions asked.
∞•*˚ Βгįťţαňγ ˚*•∞
It is not enough to know how to ride; one must know how to fall.