There are plenty of people who have left the Bujinkan who retain my respect as martial artists and as men: Doron Navon, Quintin Chambers, Jeff Sherwin, Stephan Marcec, Chuck Dervenis, and so on. Martial arts are all about finding what *YOU* need.
The problems I have expressed with some others who have left the Bujinkan is their actions after leaving or their reason for leaving.
(1) Some, despite supposedly going their own way, continue to emphasize their relationship with Hatsumi-sensei in trying to sell their "new way." If it's not Bujinkan, it's not Bujinkan period. Don't say that you are teaching Bujinkan, when, in fact, you are teaching some chimera art. If you want to do some chimera, or train completely in another art, then call it a chimera and go for it!!! You have my complete support! But don't call it Bujinkan.
(2) Some have shown through their actions or words that they lack integrity. Some have outright falsified their training experiences or knowledge. That's a no-no no matter who you are, imo.
(3) I personally think it is stupid to stop training in an art merely because you don't think others deserve their rank or don't understand certain things. Martial arts are a personal pursuit. To stop training in an art merely because someone else doesn't see the same things you see in your own training is kinda silly, imo. But that's just my take.
I'm certain that if you were to go back and look at my comments/arguments regarding particular individuals over the past decade, you will find that they map onto one of these three core ideas.
Hope that helps!
-ben