Removing a side mirror

You mean to tell me that you can't unthread that metal clip from the mirror adjuster? Looks as though you could.
Lol! With all due respect, you make it sound like child's play. Fat chance of that. Those sharp spring steel tabs are dug into those softer pot metal threads, and with a little corrosion to boot, it would not be as easy as you make it out to be; however, Cudamark and Dana67Dart are on to something.
Plus, it's in an awkward place to get to.