Assuming the fact that he is an actual master, and the first American to be allowed to run an Aikido dojo in Japan, I'm fairly sure he's not a fraud. Just because he's a fat actor now, doesn't mean he wasn't, or isn't, a serious Martial Artist. Any of you nobodies that thinks he's a fraud need to GTFO.
most people don't understand what this means, when you know a little bit about japanese culture (I used to live there, in the actual part of town where he got his Dojo btw, pure coincidence), you realize that if they let it run his dojo in their own country, it probably means that he's one of the greatest of our, if not all times in his discipline.
that being said, when machida mentions him in the interview, you can see him and rogan smiling like it was some sort of private joke.
so really it's hard to tell, I want to say Segall is legit because hard evidence (having his own dojo in japan is hard enough to me) suggest he is. Being an actor might just have been a pleasant way for him to make a living out of his art, there were no UFC back then and I'm not sure running a dojo puts someone in a very comfortable situation, not as much as being a semi successful actor anyways.
so all in all, I think
1. he's legit and is actually coaching guys at blackhouse
2. they're over-using his notoriety to play it as a joke while truly, it's not
I actually seen a vid lately of rogan teaching GSP a kick, so segall teaching anderson and machida something, why not. He's been a dedicated martial artist his whole life
I'm sure there is no such kick in aikido but it's also safe to assume that segall didn't learn only aikido in his life. he could pretty much be very good in some other martial art.