First of all, I give David a lot of credit for agreeing to such an in-depth interview. That says a lot about him as a person, being willing to open up like that.
I never knew why he left the show, but I never imagined anything like that. Can't blame him one bit for walking out. Matter of fact, I applaud him for it; standing up for himself and refusing to take their crap. As for Saban calling in the rest of the cast and asking them about his sexuality; that's just fucked up. It's not even legal to do that. Or at least it isn't in other jobs. I assume television wouldn't be any exception.
I agree with him about maintaining a cast longer than one year. That does make the show better in my opinion, watching the same characters grow and change over the years. I get why Saban (and Toei for that matter) doesn't do that anymore. It makes sense, but still. Keeping them on long-term gives the audience more of a chance to form attachments to the characters, which to me is important.