What if I said I don't want my significant other to start drinking?
Why don't you want them to drink?
Drinking is bad for you. I don't want them to be drunk all the time
If they want to have a drink from time to time you should let them. They can control their drinking in moderation.
I know what's good for them. Being drunk every weekend is not healthy.
I understand that you are trying to look out for them, but there's nothing wrong with drinking within your limits. You shouldn't try to tell them what to do.