The spec says: "If a device is of a type that Ubuntu Touch does not currently work with, it should be present (so that you don’t think there’s a problem with the hardware) but greyed out." <https://wiki.ubuntu.com/Bluetooth#Listing_devices>
Given that, I don't understand what you mean by "disable the pairing button". Since the item is greyed out, you'd never get to the dialog with the "Pair" button in the first place.
The spec says: "If a device is of a type that Ubuntu Touch does not currently work with, it should be present (so that you don’t think there’s a problem with the hardware) but greyed out." <https:/ /wiki.ubuntu. com/Bluetooth# Listing_ devices>
Given that, I don't understand what you mean by "disable the pairing button". Since the item is greyed out, you'd never get to the dialog with the "Pair" button in the first place.