Michael Reagan has always been a troublemaker (not unlike his son Cameron) and opportunist of the first order to prostitute his adopted surname for his own profit. People go on about Ron being nothing more than a dancer or dog show commentator but at least he has a career based on something other than who his daddy was unlike Mr. C-grade Talk Show Host.
Ron has no talent, and he's annoying. Any accomplishments he can speak of were bestowed on him because of his last name. Up to and including the part-time gig on Animal Planet.
And Michael has at least as much claim to the Reagan last name as his step-brother.