When I proposed to my wife, it was in public, but it was well after we already discussed getting married, though I proposed to her at random just to keep her surprised. Though I can see the point OP is trying to make, there is a simple solution, "can we talk in private?". If the man who's proposing like a dick about being in public, then in kind of reverses the situation, because who knows, you can love someone without knowing you're ready to marry them, right?