I have argued that when people hear the word "autopilot" they think that it's very advanced. You argue that technically, something that just keeps the wings level is also an autopilot. I agree! I just disagree that the average person would know enough about the finer points of what a particular word actually means versus what just about everyone thinks it means.
Finally I would argue that if just about everyone thinks that a word means a particular thing, that's what it means. It might technically be incorrect, but words are just noises that people say to convey an idea from one brain to another. If you know what someone meant well enough to correct them, they probably used the word correctly.
Here's a major news website reporting on what an autopilot is and is not in the wake of the germanwings crash about a year ago. It maintains that autopilots on commercial jets (what people tend to think of when you say "airplane" or "flight"). This was the 3rd or 4th google hit for the phrase "what is an autopilot" http://www.cnbc.com/2015/03/26/autopilot-what-the-system-can...
I fully agree that if just about everyone thinks a word means something, then it means something. I'm not trying to argue based on some technicality. What I am arguing is:
1. I'm not at all sure that this understanding of "autopilot" is as ubiquitous as you say it is.
2. Even if that understanding is nearly ubiquitous, I can hardly fault someone for using "autopilot" to mean something simpler if they are doing so because they are familiar with actual autopilot systems and are naming by analogy to the systems, not to popular understanding of the term.
3. If people really do all think that "autopilot" means a fully autonomous system, the fact that no such thing is found on real airplanes means that they're a bunch of idiots, and I'd really like to know where that idea came from.
I keep talking about the simple end of what "autopilot" covers and you keep countering me by pointing out the advanced ones. I'm not denying the advanced ones exist, I'm just pointing out that the simple ones exist too, so using the word "autopilot" for simple systems is entirely appropriate.
I'm not terribly interested in the legal aspects of it, I'm just curious where everyone got this idea that "autopilot" implies autonomy (if in fact everyone does have that idea, which I'm not sure about), and I strongly disagree with your assertion that using "autopilot" to describe Tesla's system is "torturing language," given that using "autopilot" to describe a simple wing-leveling system is perfectly acceptable.