Remove contacts from synced Exchange account, without removing them from the server

How can I remove contacts from accounts I don't sync with anymore? Without being afraid of removing them from the "source" exchange account now or in the future? **Background:** When installing the email synchronization with Exchange, I thought it was a good idea to also sync the contacts. Now the internal memory of my phone is stuffed with thousands of contacts I don't really need. It seems I cannot move them to the SD card, so I want them gone. When I stop the synchronization (only contacts) with exchange, the contacts are not automatically removed. I'm a bit afraid that if I remove them manually, and click or accidentally enable the sync, the contact will also be removed from my exchange contacts list, that is linked to my companies contacts list. BTW: I know some Java, so if necessary I can develop an app to do this.