Everything can be justified by national security. You can't try and block something with "an end-less series of law suites" if the defending party doesn't even need to provide any kind of proof. "Why are we MTiMing HTTPS? This is un-constitutional! -- Because internet is a threat to national security which in turn has higher priority than your rights, Citizen!. Everything else is classified and will be discussed in a closed court." Take a wild guess what that court is going to decide...
Aren't some US providers (Comcast, Verizon?) injecting nasty tracking/advertising into HTTP pages?
That's extremely worrying as well and it appears politics so far are unwilling to make it illegal. There needs to be more protest and more competition so consumers can vote with their wallets.
And compromising HTTPS in places with a functional judicial system (and human rights) would probably be blocked by an end-less series of law suites.