Problem: When you use your Apple TV's remote, your Mac responds to the command (e.g., iTunes launches and plays a song).
Solution: Follow these steps
1) Go to System Preferences / Security & Privacy / Privacy
2) Click on the Lock icon
3) Type password
4) Click on Advanced...
5) Check the "Disable remote control infrared receiver" option
6) Click on the Lock icon
7) Close the System Preference window