Porn lead to sex addiction which lead to diminishing productivity and unhappy relationships making it the cancer of society.
I am going to take this as an axiom and assume its correct for this discussion. Its not, its completely wrong im sure, but to save time lets just assume it is right for the sake of argument.
Smoking lead to cancer which lead to early death making smoking morally wrong.
Smoking isnt morally wrong, nor is early death. Why would something automatically be morally wrong simply because it results in a earlier death for you, thats your choice, its your life. It may be a bad decision, but that doesnt make it an immoral one.