I'm curious, are there historical factors that lead to AAVE or ebonics to be seen as "illegitimate" or "slang" in the eyes of mainstream America? A quick Google search on ebonics brings up a bunch of forum posts of people deriding it as "not a real language", and as far as I can tell (obviously not scientific evidence, just personal anecdotes), the average American doesn't consider it a dialect. Is this racial in nature, or have there been incidents in the history of the USA that fostered this viewpoint?

Thank you!