One of the biggest issues I have with "self defense" against mobs is the highlighted portion of your post.Again I say, the legal implications would take a backseat to survival in a life or death situation such as suddenly getting caught up in mob violence.
So, the way someone would get "suddenly caught up in mob violence" would be to have a large violent mob sneak up on them while they were, say, unwittingly in a prime protest area during a time of widespread unrest and distracted due to reading a book on nonviolent conflict resolution?
A person worried enough about safety in mobs to carry 2 pistols, all the mags they have, and two knives all while wearing body armor could make their life a lot easier by just staying away from mobs and the predictable areas where they form.
For example, the guy who was arrested for pointing his AR-15 at a crowd didn't even live at the scene! He had taken his gun and INTENTIONALLY gone to find the protests.
I'm not saying it's totally impossible that one might get messed up in a situation that spiraled out of control in a way that prevented them from getting away. The problem is that while nationwide coverage is on just about all the time and it's well known that the protests are tending to center around the downtown of large urban areas and that they tend to get violent as night approaches, it's hard to argue that: "Ooops! How did that happen? Here I am with my body armor, and my AR-15 in the middle of a protest in a large urban area and I can't get away. Now (as opposed to when I voluntarily came down here armed to the teeth) I'm suddenly so afraid for my life that I have to start shooting into the crowd to make my escape."
If you're going to talk about a scenario, it needs to start with a plausible method for ending up in the scenario. Someone who kits up and goes down to "see them there protests in person" is not going to be treated the same as a person who lives in the middle of a protest area and is trying to escape after, say, the apartment building where he was living was set on fire. Even that's not especially plausible as the "protests" are nearly exclusively focused on government buildings and businesses.
But yes, a person forced to flee from their residence who can't do so without using deadly force is going to get a very different view of the justice system than the person who drives into one, dismounts all kitted up, and then starts shooting when things predictably get ugly. I'm not saying that a person fleeing their residence in the face of a mob is going to have an easy time of justifying shooting into a crowd having publicly admitted in advance to intentionally picking a caliber that will penetrate through the target into someone behind them (as was mentioned above)--or even shooting into a crowd in general, but they at least have a chance.
People who want to go armed to potential mob situations need to apply for an LE job in a large city and bide their time.
The rest of us who are concerned about the danger from mobs just need to follow The Rules of Stupid: "Don't go stupid places at stupid times with stupid people to do stupid things." Unlike regular criminals who are highly mobile and low visibility, mobs are not very mobile, they inevitably form in certain predictable areas, they are very visible and tend to garner huge amounts of media coverage.