In the configure dialog there should be an option for using single click in the Icon View, or it should be used, because it is nicer that way and double clicking the category icons makes not much sense.
Then don't set the double click behaviour option which is off by default.
But other desktops use double click too, but not for the settings category icons.
We have a setting for double click to activate icons. That is off by default. If you turn it on then it's on, if you leave it off then it's off. Having an options for some areas and not others does not make any sense.
*** This bug has been marked as a duplicate of bug 377309 ***