"Smoking is different, when used properly and as intended, your smoking harms the person next to you" - Not proven, if you want to take it on faith you can believe what you want but studies have failed to prove this conclusively
Secondly, when used properly and as intended, firearms harm something, somewhere, maybe not a person, maybe not next to you, but their uses are somewhat limited.
While I am posting on this topic I would also like to point out that this has nothing to do with second amendment freedoms. These weapons can be produced at will by private citizens. This means if it comes to a revolution (and honestly, I don't know what you are all waiting for), they can be produced at the time when needed. At this point the government is going to kill you on sight anyway, so whether you are breaking gun printing laws or not is irrelevant.
If anything, 3d gun printing makes the second amendment obsolete. If 3d guns were any good (currently they aren't but maybe one day), the need to keep arms would no longer exist, people would only need to have 3d printers in every house and could make the guns the day before the revolution starts.