For developers: Delete forum groups
To delete a forum group, you must perform the following:
    - Get an instance of the manager.
    Get an instance of the ForumsManager object. 
    - Get the specified forum group.
    Get an instance of the forum group. For more information, read For developers: Query forum groups. 
    - Mark the group for deletion.
    To mark the group to be deleted, call the DeleteGroup method of the manager and pass the group as argument. 
    - Save the changes.
    To delete the group, save the changes to the manager. 
NOTE: To delete multiple groups, query them and execute the code below for each group.
NOTE: If you try to delete a group that has forums in it, you will get a Telerik.Sitefinity.Forums.DeleteForumGroupWithForumsException exception. Before deleting the group you have either to remove the forums from the group or to delete them first. For more information, see For developers: Remove forums from forum groups.
Following is a code example: