1. Using the Microsoft SQL Management Studio tools connect LyncServerName\RTC using an account that has full CSAdministrator rights.
2. When connected, under databases right click "RTC" and select "New Query".
3. In the new query entry fieldtype the following:
DECLARE @RC int
DECLARE @_Owner nvarchar(4000)
EXECUTE @RC = [rtc].[dbo].[ImpDeleteContactGroups2] "email@example.com"
4. Under the Execute command detailed above change the users SIP address to be the desired one. To run this for multiple people at once, add more Execute lines for each person and then click Execute in the tool bar to run the script
5. Once the query has run, log into the Lync 2010 client as the user(s) and ensure their contacts list is now blank.