I can’t speak as a linguist or even as someone familiar with Ebonics. I will speak as someone who paid his bills for a few years by telling jokes to drunk people in dark rooms (which is, for most, a truly miserable existence, but that’s a rant I’ll never write).
I agree with the premise that if you’re going to do a parody of anything you should begin by understanding your subject, and that if you don’t you risk irritating or offending those who do. Worse, from the comic’s perspective, they won’t laugh, the club owner will hear silence, and the next booking becomes less likely. Playing with dialects carries two added risks: it inherently mocks whole groups of people (the butt of the joke becomes not only the guy you’re talking about but everybody who shares that manner of speaking) and they are very hard to do correctly. Further, if done incorrectly, the source of the humor is not some true and funny characteristic of language (which is dangerous enough) but a false stereotype, which is a close cousin to catering to bigotry for laughs (and by extension, money), which is in my view reprehensible. I never attempted any dialect on stage just because I judged the risks to be too great, my skills inadequate, for a paltry return (I’ve only known one dialect-based joke that I thought was funny).
That said, most comedians I’ve known are concerned mostly with two questions, in this order: 1) Did I get paid? and 2) Did they laugh? I knew very few comedians of the Will Cuppy school, who would do extensive research on a subject before joking about it. Many routines begin as a random ad lib thrown out one night that happened to get a laugh, and continued to grow until the point where an audience stopped laughing. Comedians aren’t theorists, they tend to be practical when it comes to their routines. If you see one get a five-minute shot on TV, you can bet that he’s using material that has done very well in the past.
Which is sort of the problem. There are plenty of venues where the audience is as ignorant as the comedian, and will laugh at a parody that would bore, irritate or offend them if they knew more. I played in front of lots of different kinds of people, from black urbanites to military personnel to offshore oil-rig workers to white bankers to schoolteachers to retirees to bikers, etc., etc. But I very rarely played to a single room that was particularly diverse. This may not speak well for society as a whole, but it’s easier by far for comedians. Trying to tell jokes to a truly diverse crowd would be like trying to lecture in seven languages at once.
What I’m getting at is that I think there are plenty of audiences for whom a random sprinkling of “be’s” is enough to evoke the concept of Ebonics so they can follow the joke. That comedian will learn, the first time s/he plays to a larger or more knowledgeable crowd, that it isn’t always enough. Unfortunately, the poor slob on stage sees the people in the room, not the people watching him on TV, so the feedback is imperfect.