Admit it. It feels icky and wrong to say "It's okay to shoot yourself in the head". There's a part of you that feels guilty for writing what you just wrote. What if a child reads that and starts shooting themselves in the head because of what you said?

"It's okay to eat rotten food that has mold growth on" "It's okay to stop breathing air" "It's okay to tan using a UVC lamp" It's okay to jump off a skyscraper"

The only reason why you consider one question (smoking) to be a moral issue instead of all questions is because you want to smoke. You're not saying jumping off skyscrapers is a moral issue, let along the infinite other questions not listed here.