Back in November, 2011 Joseph wrote about the new feature in Aperture 3.2 that added a new Auto-Curves behavior, and how to get Curves to act like it did in the previous version. As it turns out, if you don’t want the S, just option-click.
To take this even further, it’s possible to removes individual curve points with a control-click.
Removing a Curve Point
To remove a curve point just mouse over the point in question and control-click. When you do, an action window will appear giving you the choice to reset the entire curve or to just remove the selected point.