There are are thousands of transmissions passing near/through/by you at any moment, it doesn't mean you have rights to intercept and respond.
Do you transmit on Police frequencies? Do you transmit to Air traffic control? Do You transmit to military bases?
No? Why not?
Because you are not authorized to do so. Just because you receive a transmission doesn't give you the right to TRANSMIT in response.
Come on! You're being silly. Transmitting on a ATC frequency makes that frequency unusable for its intended purpose for the entire time (plus a bit) during such a transmission. Drive-by wi-fiers checking their email do no such thing.
ML/NJ