Lungri,
I have a script that would assist in the bulk removal of users. This script would not have the same adverse side effects as removing the user from the database as it uses the Site Admin API to remove the user instead. This would be the same as if you actually clicked the remove button in site admin. To use this, populate a list of users you would like to remove in an Excel document, then execute this script as a macro (be sure to input your server URL and site admin login info).
Public Sub RemoveSiteUser()
Dim rCount
rCount = ActiveSheet.UsedRange.Rows.Count
Dim qcServer, qcUser, qcPassword, UserId
qcServer = ServerURL
qcUser = SiteAdminUser
qcPassword = SiteAdminPass
For i = 2 To rCount
UserId = ActiveSheet.Range(''A'' & i).Value
Set objSA = CreateObject(''SAClient.SAapi.9'')
objSA.Login qcServer, qcUser, qcPassword
On Error Resume Next
objSA.DeleteUser UserId
If (Err.Number = 0) Then
ActiveSheet.Range(''B'' & i).Value = ''User Deleted''
End If
On Error GoTo 0
objSA.Logout
Set objSA = Nothing
Next
End Sub