That's nonsense. You can start a bond rating agency tomorrow. It just won't mean anything because no one will trust it and you won't be in a position to demand access to company internals to inform your ratings. And the SEC won't recognize your ratings (it has recognized additional firms in the past, but it's nontrivial) which means for a lot of regulator purposes your ratings have no effect.
If they got rid of regulations tomorrow, the first barriers to entry would keep you from starting a ratings agency anyway.
If they got rid of regulations tomorrow, the first barriers to entry would keep you from starting a ratings agency anyway.