Can I unload com.apple.mrt via launchd or otherwise remedy these errors?
If you want to rid yourself of com.apple.mrt, you can run a few Terminal commands to get it out of your hair.

First, open the Terminal app. You can find it in Launchpad or by using Spotlight. Next, stop the process using sudo launchctl stop com.apple.mrt.

Then, remove the components, using the following (or manually remove them in Finder):

sudo rm /System/Library/LaunchDaemons/com.apple.mrt.plist
sudo rm /System/Library/LaunchAgents/com.apple.mrt.uiagent.plist
sudo rm /System/Library/CoreServices/MRTAgent.app
sudo rm /usr/libexec/MRT


Finally, reboot your machine. com.apple.mrt should no longer launch on startup (or at all).

Notes:


You may need to enter an administrator's user and password.
Apple may release updates which re-add com.apple.mrt to your machine.