I can't add much that's already been said. My question is, why? Why would they do Ragtime if they didn't have the actors for it? That's my question with many white-dominated theatre groups that require more ethnically descriptive parts. Stick to what you can do.
I mean, I'm sure Ireland would be mad as all hell if an all black troupe in white face did "The Pirate Queen" or "Riverdance" or something, because it would look like they were mocking Irish people.
It doesn't seem to me that they're intending to be racist, at least I don't think they were, and mock the minorities-but it's really the connotation of blacks being ostracized in the theatre, as they once were.
My philosophy is, if you don't have the group to carry the production, don't do it. There's many great shows out there. For instance, at my school this year, the only reason I would consider doing "The Wiz" is due to the fact we have a large black population. I don't mean to sound racist; but I'm trying to pick the shows that would be more suitable for the audience and the performers, and many of the kids sing in their baptist church choir, and "The Wiz" music is very akin to black gospel music in some ways.
On that note though, it doesn't really annoy me when all-white groups do "The Wiz", because it's usually all in good fun--but then the message of the show kind of gets lost. "The Wiz" is really about identity in a lot of ways, something black people were still trying to find in America during the 1970's, just getting out of all the race riots and such in the decade previous. Most shows that have black characters are usually written for black people for a reason, there's usually a reason for it.
Interestingly enough, I saw a production of "Rent" recently--a school version, where every one of the leads was white (is that proper grammar? Was white?), there were two black people in the ensemble, a few asians, and I think one Indian girl, but I think that was it. And all of them actually did really well, for the most part. I mean, it felt like there was an element missing with Angel or Mimi not being hispanic or Collins, Joanne or Benny not being black--but it just kinda proved "Rent" is the kind of show that still really does work regardless of racial barriers. Race is not a very important part of "Rent", in my opinion. Very few times are the character's ethnicities really raced. I know Mimi mentions hers in "Out Tonight", and I feel like somewhere Collins or Angel mentions theres, but it's not really important.
I think color-blind casting on the whole is acceptable, but it really depends on the show and if race is a big factor in it.
Recent Broadway and Off-Broadway:: Carrie, Merrily, Ionescopade
Next On The List :: Clybourne Park, Once, Streetcar, BOM