Healthy skepticism is useful, but if you think that the editor-at-large of a well known U.S. media publication would conduct a public hoax involving her son, well, you do you.
What I mean by the second part is when you come up with a reason to question a claim, that doesn't automatically weaken or invalidate the claim. Your first contention is basically "how can it be racism from just a craigslist posting?", that is, how did the assailants know he was black? Well, it's possible the assailants became more aggressive at the time of the meeting, after seeing the seller was black. Or perhaps the seller included a name more common with people of color. This is not suggesting that either absolutely is the case, but they are both likely and not uncommon scenarios in the present day. If you're going to begin speculation in this manner, it is only fair and reasonable to consider how your conclusion might also be falsified, considering alternate and equally plausible scenarios.
Or in the case of the cuffs, for which your comment seems to rely more on a rather dismissive statement of ignorance - cuffs certainly can and do cut and tear into skin when not used properly. Just do a quick image search for "injuries from handcuffs" (warning, some images on this search are nsfw and unpleasant) and it's plain enough to see multiple examples of damage from handcuffs, whether it be bruises or lacerations - it's fairly hard metal tightened hard around a fragile point on the human body. It's not hard to imagine how that could do damage or how bad the damage could be when used improperly (Intentionally or not). Yes, it is important to get this verified (a picture from the author would do nicely), but the basis of your skepticism is not really set in reality, but seemingly in raw skepticism.
The point I'm trying to make is that it is good to withhold judgement, but the attitude and the questions you raise really aren't sound, and instead appear almost vindictive.
Be skeptical, but part of that requires being a bit dispassionate and openly considering reasonable possibilities. It does not mean building up speculation as the foundation for a conclusion. It is possible this is a hoax, as you say. But to suggest it "screams" hoax is inaccurate.
You can't know it is a weapon. It is on your back. I've never been handcuffed, but they can hurt.
I have, however, been surrounded by cops taking folks home. Some friends of the dude I was dating, and we happen to have different skin colors. 4-5 cop cars, lights, drug dogs in a small public housing parking lot. I start getting questioned about drugs, and expected me to know a lot about my passengers. "People have been doing crack here, and we've found out white people are doing it too". I was let go, and to this day I hope those dudes were ok.
I've been pulled over for swerving after a lane change. Dude said we were drunk, even after we passed the breath test. It was late, we were driving around talking, but happened to be in a mostly poor, african-american part of town and we weren't. Her baby was mixed, though. It worked, we called it a night simply because of harassment.
Had guns out once with lots of cops. I'm still not sure what I did wrong. The park closed at 11, but since it was getting dark a parks department employee asked us to leave (but not the other people). Down the road we were surrounded, guns out.
The point is that there are a LOT of these sorts of stories, and it has taken a few killing with news coverage for them to finally - 20, 30, 40 years later - for anyone to start doing anything about them.
I was lucky enough to get out of my fear of the police because I've since moved. Racism exists everywhere, but not everywhere will tolerate it from their police department. When I'm out walking home at 2am here, I'm no longer afraid of the police. I won't even get stopped asking what I'm doing out, why i'm in a neighborhood, etc. So long as I'm just walking along, everything is good... and i'm in a city of 180k people.
How did her son know it was a weapon pressed against his back?
How could the handcuffs possibly have cut his wrists? Handcuffs don't have, like, blades on them that just cut you as they're hanging off your wrists. Seems like something added to punch-up the narrative.
And then tag it with a couple "Trayvon" mentions at the end. This screams "hoax" to me.