The spoke protector is to prevent the RD from engaging the spokes and being destroyed, It isn't necessary, but for low end RDs or bikes where decent maintenance isn't expected, (like dept. store bikes) it can save the owner serious grief if, for example, he drops the bike and bends the hanger. Spoke protectors aren't a substitute for proper RD adjustment, they just help lower the consequences of poor care. If you're diligent about maintenance, you can probably live without the safety net they provide.

In the OPs case, it won't help at all. Since the RD is touching the spokes (never a good scenario) the added loss of space to the spoke protector can only make things worse. Solve the problem by finding out why the RD is touching the spokes, such as a bent hanger or RD cage, and deal with that. Then you can decide if you want the added protection the spoke protector might offer.