I feel the current system of overbooking and how it is "regulated" is backwards, and airlines should rethink. Perhaps they could do some sort of an auction without a maximum. It is their problem after all, and a market mechanism seems a reasonable way to deal with this. Sometimes this would mean someone who does not care as much will gladly take $150 as compensation. Other cases might lead to much higher numbers.
The next bit will probably not make me particularly popular, seeing most of the reactions to this debacle, but here goes.
The airplane itself is not a suitable place for any form of protest. No ifs, buts or anything else.
Once the flight personnel asks you to leave the airplane, you leave. Take the fight outside of the airplane, in court or wherever or however you deem appropriate. But not on the plane. Your work/patients/personal tragedy is in no way relevant. If you disagree with the service offered, don't use it. Vote with your feet and your wallet. Don't claim you have no alternatives or whatever. Society does not owe you your preferred lifestyle in any way.
If this guy refused to leave after he was asked to do so, according to the rules het agreed by upon entering an agreement, and I would be delayed by the ensuing situation, I would even consider pursuing some form of legal action towards him.
Having said all that, I do feel the way commercial air travel is organised these days is beyond ridiculous. I therefore avoid it whenever and however I can. If more people did that, it would have changed by now. People don't, so it doesn't. Because most just feel entitled to whatever they feel entitled to, without any basis. Fuck them.
Oh, and screw airlines too.