From "Star Trek: Voyager: Life Line (#6.24)"
[Dr. Zimmerman has proposed sending a Mark IV back to Voyager
They don't want a Mark IV. They want their friend.
No EMH was ever designed to be anyone's friend. He's just a hologram!
Is that how you feel about me? Just a hologram?
[he stares at her
I will not be ambushed in my own lab.