Unless you get a better answer. I do not really know ctsman, would it be possible to delete the other one?
In short, maybe its not possible to delete the default one. Is there a way to make the other one the default?
Did you check the documentation? Maybe there is something which can bring you further?
http://www.cisco.com/en/US/docs/telepresence/cts_manager/1_8/admin/ctm_cfg.html#wp1092407
Please have a backup in place and make sure you can revert things if you try around.
All tips are followed at your on risk :-)