Wow, so I guess they are pretty aware of the site. When I googled the GMs name last week, your original post came up on the 2nd page. I have a feeling it's a tad higher now! In my opinion, having a lawyer contact you at this point is strange. Nothing you stated was really defamatory, just a bit emotional, as could be expected.
Here are the facts though. Your images are of a warning light in your car, that's documented by your owner's manual. After being "mis-diagnosed" by the service tech, you were sent on your way. Days later, you actually are involved in a MAJOR SAFETY FAILURE in your car. Let me repeat, MAJOR SAFETY FAILURE! This is an extremely serious issue. And in my opinion, actually goes beyond the dealership, and I would contact BMW NA immediately to voice your concerns just with the safety of your vehicle. This is NOT a convenience issue, it's a safety issue, I want to stress this. The fact that the dealership is not taking the opportunity to "re-diagnose" your vehicle at this point under warranty is also strange.
Penske personnel, if you're reading this, I think if you just fix the issue, the OP would state you fixed it, you'd help diagnose a possible safety failure in the vehicle, and this would be over. That your dealership keeps up this mentality is only going to continue to bring negativity around your organization. These types of threads always find their ways to other car sites as well. You're fanning flames, that strategy almost never seems to work.
OP, definitely hold fast, keep your lawyer on speed dial, and I'd continue to attempt to work with the lawyer that called you. The GM obviously is not interested in helping you, but maybe you can work something out with this lawyer. I'd call him everyday to see if there is any further resolution. And after enough days go by, and no action has occurred, I'd ask him directly, if you were me, what would you do? Remind him that this is seemingly a major safety critical failure.
I develop medical devices for a living. We work very hard to make sure they are safe. We go through many aspects of a device to ensure that any risks to a patient are mitigated. The car industry I'd imagine goes through the same level (and probably more) making sure these vehicles have their potential hazards mitigated to a reasonable level. That a car could lose it's steering "completely" at highway speeds is such a severe hazard, I'm sure the engineers worked very hard to ensure what happened to you wouldn't. But it did, so this needs to be understood how it could happen. Is it an engineering problem? A failed part? Bad software or electronics? That a dealer is ignoring you and saying the warning you got was a state inspection is completely nauseating.