As with many topics, I would not force it upon him but rather wait for a suitable situation to present itself.
I don't think there's a "right age" for this talk, or rather that this "age" is not counted in years but in observations and questions.
In your case, it might be when he asks you what do you do at work, or simply a situation at home where he notices that mom and dad (or someone else he observes) take a glass of wine with dinner and he doesn't get one.
When he does eventually ask, have a short and simple response ready.
It's like coffee, or tobacco. It's something that only grown-ups get and something that can be dangerous. It's okay to consume (wine/chocolate/whatever) in small doses but anything can become harmful if you're not careful. (Coffee might be a stretch, but I'm not aiming at being scientific here.)
Give him time to absorb this. If he asked about the wine at dinner time, bring it up the following evening, just ask if he remembers what you said. If you're at an event where someone got a bit tipsy, or he notices a drunk person in the street, remind him of what you said about (lack of) moderation. Depending on his maturity, you can also start explaining what it is you do and how you'd go about handling a person like that.
Also, be a role model. Walk the talk. Say out loud what's common sense to you: I'd better only have a single glass of wine or else I'll feel bad. I'm sure your work gives you plenty of ideas that are better than what I could come up with here, but I thought I'd mention it.
Personal opinion: Go ahead and scare him. Why not? There's no objective benefit to alcohol, it's not something we need, so there's nothing about it that's worthy to "protect."