Mind you this is answering your question "any way to bulk delete" - it's up to you to make sure you're not deleting something you need!
On a Mac: [Users > Library > Application Support > Capture One > LCC].
From there you can rename, delete, and otherwise manage your LCCs as if they are simply files - because that's what they are. This is also how you would quickly move a large number of LCCs from one computer (e.g. your laptop) to another computer (e.g. your desktop).
If you are in Lion you may not see "Library" in Apple's attempt to protect you from yourself :-/. If so use the finder "Go" pull down and hold down "option" to see "library".
In recent versions (I believe this began around version 5, but can only say for 100% sure it is like this in version 6.3.x) Capture One places the LCC in the [Capture One / Settings] subfolder as well as the App Support folder; if you select a raw file which has an LCC applied to it and opt to remove (or change away from) that LCC Capture One checks if the LCC is in the App Support folder - if not then it asks if you want to "import" the LCC from the raw file so it can be on other raw files. Likewise when you pack a file as EIP the LCC is included in the EIP file so that if you go to another computer, remove the LCC, and that LCC is not available in the App Support folder it will prompt you if you want to import it.
