That may be the section of the Constitution THEY cite as authorization for the Drug War, but I will point out that "Wars" are fought by the Department of Defense, not the Department of Commerce, and I do indeed regard the pursuit of the drug war to be defensive in nature.
When China tried to ban the importation of opium, it was their fighting men and ships that confronted the British. Now no one can deny that they regarded their version of the drug war (which they lost) as being an ACTUAL war, one that would have consequences such as the enslavement of their citizens should they lose. Well they lost, and their citizens indeed did become slaves to their drug importing masters.
My point is, Just because Congress and the authorities are pointing at the wrong authorization for waging the War on Drugs, that doesn't mean they do not have a correct authority backing them. They do. It is the requirement by the constitution for the Government to defend the nation from attack.
If we want federal government to wage a domestic drug war, then we need to enumerate the power for them to do that.
There was no declaration of war, there is no discernible "enemy". The "war on drugs" is as much a real "war" as the "war on poverty".
In your mind that rationalization might justify the drug war, while de-legitimizing all the other abuses of the Commerce Clause, but in Washington and in the courts it will not.