Child porn is NOT non-coercive by its nature. It involves real kids who are incapable of giving informed consent to what happens to them. That is a bad example.
“Do you favor the current war on some drugs?” would be a better question, for the use of mind-altering substances IS a voluntary act. If one is over 18, the age when someone may enter into contracts, join the service, etc., there is no other issue involved. So, do you favor the current trashing of the Constitution in the name of protecting folks from themselves, AKA the war on some drugs?
“use of mind-altering substances IS a voluntary act”
The first time maybe. By definition, we cannot know whether the unaltered person would choose to do it the 2nd time, because their mind has been altered.
“If one is over 18, the age when someone may enter into contracts, join the service, etc., there is no other issue involved”
Incorrect. Contracts can be invalidated if there was coersion, or if the signee was misled in some substantive way, or if the contract itself breaks the law. Or if the person was mentally incapable of signing a contract, for example if they were high on drugs, and could prove that they were high on drugs, it could be argued that a temporary insanity existed at the time of signature, thus invalidating the contract.