This is an apt analogy. I don't think we learned anything about Parmelee's long-term prospects last year, which is why we're pretty much back to square one with him this year.
As much as I don't like Hicks' approach thus far - he is certainly capable of better - if you don't let him play through the slump, you'll never know how he responds to slumps. Calls for demotion are way premature.
Not to be a naysayer but if you leave a guy in AAA all year you still don't know who he is long-term until he faces major league pitching. You also can have a guy struggle in the majors the entire year and not know that he's washed up. There is no magic way to handle guys: some do better getting brief chances at the majors whenever there's an option, other need that sense of security with "this is my job."
The only thing we can really say with any certainty is that players need to play. If Hicks is going to be platooned, might as well send him down and let him work everyday.