Distrust
From LSWiki
Stop Trusting
Usage: stop trusting <who>
Causes you to stop trusting a person or group of people. This is only applicable to those you are trusting specifically because of having chosen to trust them; if you trust them for another reason, such as being friends with them, you must remove that reason in order to stop trusting them.
See Also: show trust, start trusting, report trust, start following, mount, touch