What about musician turned pedofile? R. Kelly Pete Townshend I'd still say celebrity turned murderer is worse, but musician turned pedofile is pretty sick.
In that case, I'll save you the grief of telling you how I feel about Reagan. I think the celebrity to murderer crossover has worked pretty well. They've been successful in their new pursuits and mostly evade conviction.
I don't have a problem with musician to athlete as much as athlete to musician. Most musicians who try out for teams have a background in the sport. Garth Brooks played baseball at Oklahoma St, Percy Miller played ball at UH, etc.