Here's your allegation:
"But the majority of speaking roles in mainstream productions are written for whites and often specify white in their casting calls"
Show me casting calls, where race is irrelevant (i.e. the actor is NOT playing Lincoln), that specify white only.
Can't get anymore straightforward.
Sorry Skip... that's impossible to do. That fact that you even requested such a thing reveals how little you know about the casting process. I don't mean that as a flame. It's simply that the nature of these casting notices (what we refer to as 'breakdowns') are extremely confidential. Actors can't even see them. they are distributed only between Casting Directors & agents. The only way actors get access is by hacking the breakdown system and file sharing amongst other actors, or if agents give them access, but for the most part actors are kept out of the loop.
Right now the best I can give is anecdotal evidence from just a few months ago. A friend of mine facebook shared an urgent casting notice posted by one of her friends (an agent) who was desperate to find 2 little girls between the ages of 8 - 10 yrs. old to play guests for an upcoming scene in a TV show depicting a children's birthday party. In his notice, he mentioned which Casting Director he was trying to locate the children for, as well as the location (address) where the scene was going to be shot.
Well, I happen to know the Casting Director for that show and she's a sweetheart. If there was anything I could do to help her out, I would. My friend who also shared the noticed is a terrific gal, and I was only too happy to help out one of her friends who was in turn trying to help a mutual friend of all three of us. Besides, I had been in that agent's shoes, so I was more than happy to help if i could. Then it occurred to me that my own nieces are 8 & 10 yrs old, live right around the corner from the home being used for the location, and they were off school at that time, so I thought, perhaps I could help to feed a few birds with one worm.
I noticed there was something lacking about the notice he put out though. It didn't specify any ethnicity, or that all ethnicities should be submitted, so before contacting my sister to see if the girls would even be interested, i called the agent to find out about it. I mentioned there was no ethnicity specified on the little girls. He contacted the casting director for clarification, and she specified the little girls they were seeking had to be caucasian. So much for that. Their search continued. He did subsequently re-post the notice specifying the little girls had to be caucasian.
Even when a breakdown specifies a role is open to all ethnicities, invariably what often happens is that only caucasian actors are called in to audition for the role. I doubt much as changed over the years, but it was a big wake up call for a lot of people when the union actually started tracking audition rates and the ethnicities of performers being called in based on union audition sign-in sheets.
And to be honest Skip, your assuming that this type of thing doesn't occur is just ignorant. I'm not trying to insult you, you just don't know because it is a world foreign to you. Your above comment is the equivalent of someone saying to a professional bodybuilder... that's bullshit when you say you have to eat the extra lean ground beef... there's nothing wrong with you eating the cheaper ground beef with all the fat in it. Or what do you mean you have to eat all that food, or that frequently. If you don't work in that environment, you don't know and have no business assuming what is or isn't common practices with such adamance