Bluetooth is a peer to peer network creating interface whereby devices are specifically paired upon request. When Bluetooth is enabled on a Mac, it is always on to be able to connect to previously paired devices or pair new devices. If a new device was being paired that you didn't initiate, you're being given a chance to cancel out once or forever ignore that device. That means that ignored device will never be able to connect to your Mac again.
If anything, that should bolster your confidence in the technology since steps have been put in place to put you in the driver seat of how devices can connect to your Mac.
Second, Bluetooth is broken into many different types of profiles that have very narrow use cases. Keyboards/mice use the HID profile. Headphones use the handsfree audio profile.
A lay person would never know the various components that make up Bluetooth, and UNLIKE WiFi, just having Bluetooth doesn't mean you can do a LOT of things with it.
Learn about technologies before making abrupt decisions about them. AND if you truly mistrust a technology, then make no exceptions and turn it off.
