Do not allow idea category parents to be selected

I have categories setup but the parent category is also a selection in the menu. I want the parent to act as the group header and only the child elements to be selected. 

Example: 

Bug:  Web, EDI, Local client

Enhancement: Web, EDI, Local Client

Current behavior allows submitter to select BUG as a category.  We want the users to select the channel within the group of BUG. 

I can replicate this behavior on your own idea portal.  I've selected the main group "Ideas portal" instead of a child in the list.