This time, the TSA manager for MSP told me that the TSA is above the law. Yes, in that many words.
If you have sleep apnea, and carry your CPAP on with you instead of checking it, they will search that bag. Period. This is a directive from the TSA in Washington. They claim that it's necessary because of the motor inside.
What this means is that anyone who has sleep apnea - a medical condition - will be singled out for special TSA attention because of their condition. If they don't want to do that, they can either check their CPAP or leave it at home. The former is unacceptable because the airline could lose it (and the airlines themselves recommend not checking medications, in the same class as this machine) and the latter is unacceptable because, for many folks with sleep apnea, it is the only way they'll get a good night's sleep.
I have no idea how to raise enough hell to get this one reversed, but I'm going to start trying.