Because when you seek to ban reading and smoking (tobacco) materials because "it's good for us," your are infringing upon the individual right to choose a behavior that interferes with NO ONE else's rights. It is a form of majoritarian tyranny.
.... Are you sure it's not you who are forcing your morality on me?
Most assuridly no. No one is trying to force you, or your children, or anybody who is morally opposed to smut to buy it or view it against your will.
[snip]
This man did not live and die in this land so that men could spend their lives jerking off.
Nor did Lincoln live and die so that you can dictate to others what they do with their hands in the privacy of their own homes.