First I can't see any value in getting a commercial license but obtaining the appropriate operating license for your motor home is simply good sense. Imagine the field day a below average attorney could have if you were involved in a minor bodily injury traffic accident and you were not properly licensed to drive your 24 ton Prevost. Better have a BIG umbrella policy! I am surprised that the insurance companies don't require the RV license. Secondly, I think the anticipated response from law enforcement is grossly overblown. I haven't been stopped for a traffic violation for almost 18 years and have never had a moving violation. Trust me, that doesn't mean I always drive in full compliance with the law! About 5 years of my 69 year life was spent as a class 'A' commercial truck driver. It seems to me that the treatment difference from a 'C' license to a RV or 'B' is going to be negligible unlike how one may be treated with a commercial or 'A' license.
In summary, if your state requires an RV license for the vehicle you operate I think you will avoid a lot of headaches by complying with the law. That doesn't mean being "over-licensed" but with the RV permit the secure feeling when you hear a siren or have a close call is worth the minor effort required to obtain the license. I also agree with Jon about gaining some knowledge while studying for the test. Furthermore I agree with Joe C. I am glad I no longer need a class 'A' for my job!