Remember to pack afterwards, or the tags will still be there, just not usable.
Another method that I use when adding or deleting a large number of Citect tags is to use Excel.
Make sure you set the Dbase setting to Dbase 3, and when you open the Excel file, select all and change the format to text. You can then add or delete masses of tags quite easily. Do not accidently save to Excel format or you have to start again.
Remember to pack again after you finish, then compile to look for errors.
It is also a good idea to backup your Citect project before you start deleting tags, you may find one or two are still being used.
Hope this helps,
Doug