Hello Steven,
Thanks for using Apple Support Communities.
As I understand your post, music in iTunes will just spontaneously start playing on your Mac. Does this happen when you use the remote for an Apple TV? I'm not sure what you mean about turning off the IR receiver in the setup, but you can actually disable the IR port on your computer in the Security & Privacy section of your System Preferences.
Choose Apple menu > System Preferences, click Security & Privacy, then click General.
Click the lock icon to unlock it, then enter an administrator name and password.
Click Advanced.
Select “Disable remote control infrared receiver” to turn off IR reception, or deselect it to turn on IR reception.
To set your Mac to respond to the commands of a specific remote control, click Pair, then follow the onscreen instructions.
OS X Yosemite: Turn infrared reception on or off
Take care,
Alex H.