Wired headphones activate OK Google detection when listening to audio

Go to Google Feed>settings>voice>hands free

turn off for wired headset
 
Odd. Are you in the correct screen?

Another way to get there:

Pull down the notification shade, hit the gear icon to get into settings.
Scroll down and select Google.
Scroll down and select Search.
Scroll down and select Voice.

Once there I see Languages, Ok Google detection, Hands-free, Speech output, Offline speech recognition, Block offensive words and Bluetooth headset as my options.

Tapping Hands Free gives me two options - allow requests with device locked for Bluetooth and for Wired Headsets.
 
Odd. Are you in the correct screen?

Another way to get there:

Pull down the notification shade, hit the gear icon to get into settings.
Scroll down and select Google.
Scroll down and select Search.
Scroll down and select Voice.

Once there I see Languages, Ok Google detection, Hands-free, Speech output, Offline speech recognition, Block offensive words and Bluetooth headset as my options.

Tapping Hands Free gives me two options - allow requests with device locked for Bluetooth and for Wired Headsets.
Right. There is no way to block the wired headphones when the device is unlocked.