I can see how you could differentiate the two, but differentiating the two requires making one's own rules about what kind of "magic" (for lack of a better word about forces that can't be observed, measured or reasoned about) is sensible and realistic and what kind of magic isn't. Which is still a lot to swallow for someone who doesn't share your rules.
In other words, I think it's fair to say, "It's internally consistent to believe in curses but not jinxes," but it's also fair to say, "Even if it's internally consistent, you still need a layer of arbitrariness to reach that consistency."