It's called common sense. Do you know nothing about how criminals operate? Putting effort into setting up a Craigslist ad for an expensive product and ambushing the victim implies that robbery was the motive. Do you really think that the suspects would have called this thing off had the buyer been black or Hispanic?Oh really? I seemed to have missed that piece of information. Would you mind showing me the evidence that what you say is a fact and not your opinion?
There is nothing about this case which suggests that the victim was targeted based on race. If they were exclusively targeting white people there are numerous ways to do that, and Craigslist is not one of them.