Hi,
I may be wrong but I think we are missing the biggest part here.
There is indeed something greater that the direct vote of people and it's called Human rights.
As long as human rights are opposed to any law voted by the people there will be not problem at all.
A constitutional controle might be as well a way to stop some abused in the field of public health code for exemple.

The people don't always choose what is right for himself in the field of health and in the field of justice.

Justice of the mob and medecine of the moab can't be allowed even by the suprem power of direct democracy.

To illustrate my statement :

Medecin of the mob : [www.youtube.com]

Main comment :
"Don’t like gay marriage? Don’t get one.
Don’t like abortions? Don’t get one.
Don’t like drugs? Don’t do them.
Don’t like sex? Don’t have it.
Don’t like your rights taken away? THEN DON’T TAKE AWAY THE RIGHTS OF OTHERS."

Justice of the mob : [www.youtube.com]

Main comment :
"this is what happens where there's no DUE PROCESS"

Thank you.