How do I uninstall plug ons....

If we're talking about Windows, then first see if there's an uninstaller for them in Control Panel>Programs and Features - some do, some don't. If there isn't one, then go to your plugins folder (the paths are shown in Audition's Plugin Manager) and delete the appropriate ones there - they are either .dll files or VSTs. When you've done that, you should be able to rescan your plugins Audition, and they should not reappear.

Of course if you don't want to go through all of this, you can easily make them invisible - take the check out of  'Enabled' next to the individual ones you don't want to see. The process should be similar in a Mac, I would have thought.