If you have WHM. Go into it, and click packages in the main screen. Click add new feature list. then find urchin, and unselect it. Then go to edit acounts, and set that person's account to the new feature liist without Urchin on it.
To remove Urchin as a package when using cPanel, you need have RVskin.
I only use RVskin when creating different "packages." This gives me much greater control in what I want to offer in package A or package B.
If you have RVskin, look under Configuration > Package-Feature Manager, select and edit. This will edit the entire package so you will need to create a custom package. But from the sounds of it, you may want to globally remove Urchin anyway...