Without my being there to substantiate or know the full details, we all know that there have been a ton of issues with how Disney is utilizing the Muppets, mainly evidenced with how they tried to make the TV show work, and then work again, without any success. I would imagine it being very frustrating for someone like Steve (and probably Dave as well - I'd love to hear his take on all of this) who had been performing since the late 70s and who was so entrenched with what the Muppet spirit is all about. It would appear that a lot of the people given the reins for most of the Muppet productions has seemed out of touch with that spirit, something that made the TV show fail so miserably. Is it Steve's place to fight that fight? I don't know, but I do admire his attempts to keep the true spirit of the Muppets alive and active. I can't speak to his methods, though, and if he crossed lines, there likely could have been better ways to do it. Passion can be a ***** sometimes and make even the most collected people lose it, so who knows?
All this in saying, if word is getting out about him sending angry emails to higher ups regarding the creative direction of the characters, I can't totally blame him. There's a similar situation going on now with Frank Darabont and his being forced out of work as the showrunner for The Walking Dead after the first season, also reportedly because of his attitude towards producers and execs whom he felt were totally out of touch with what he was trying to do. Steve was obviously not the showrunner for any Muppet productions, but I understand why he feels he is an integral part of the company, by virtue of having been, in fact, an integral part of the company for so long.
I can see both sides, and there's little that isn't depressing about this.