Personally I could never enter a commitment like marriage with a "one strike and you're out, no discussion" rule attached to it.
You should probably know that the only reason it's come to this is my own behaviour.
And it's a case of 'one MORE strike and you're out'.
1. I let him fall in love with me and didn't tell him I was a drug user until years into the relationship, despite knowing his attitude on drug use and that if he'd known at the start he wouldn't even have considered me for a serious relationship.
2. Even so he was (reluctantly) prepared to tolerate occasional use, only I then kept pushing the fact in his face for whatever perverse reason I don't even understand myself.
3. I broke his trust completely when visiting my (junkie) friend one time. He wasn't comfortable with me seeing him because we'd usually use together. I promised him that I would not be using during my visit and broke that promise the same night. He nearly left me then.
4. One time I managed to overdose during a phone conversation with him and it caused him to basically have a breakdown at work, in front of colleagues he absolutely despises who don't need any more ammunition.
So basically I've stretched his goodwill to the limit and have comprehensively blown whatever chance I had of him making allowances for me, and any tolerance he might have ever had for drug users. I consider myself fortunate he's still with me tbh.
Oh and lastly, he lives in a part of the world where the drug cartels are responsible for a ton of violence and misery, and druggies are the type to not just steal, but routinely rob and murder. So not exactly an unreasonable prejudice on his part.