Powerful words, no?
I'm pretty convinced that the Anderson letter is real. We know that Anderson existed. We know that the letter was, in fact, printed at the time. If someone is going to charge fraud they need to have something besides, "No slave could have written this."
That said, I'm interested in a discussion of the exact message of the letter. Better put, I'm interested in a discussion of interpretations. Most people read the letter as a sarcastic dis of Anderson's former master. There is that, but I wonder whether folks think his words of affection were more sarcasm, or sincere? I think it's reasonable to say that the part about the wages was sincere, especially given how he follows it up with hints of divine judgment and also his worrying about the safety of his daughters.
But I've found, in my reading, that the relationships between slaves and masters is often uncomfortably complicated. In numerous cases I've read about whites presuming the loyalty of their slaves, in much the way a parent would presume the loyalty of a child. In most cases, the loyalty is unfounded. But even in those cases, there is sometimes affection for the master, and in truly rare cases a kind of, almost, paternalism exhibited by the slave toward the master.