Just because the plane is smaller, doesn't make it a way of "confronting the fear in a small way". A small plane will amplify and exaggerate any sensation about flying that bothers a person (even if they weren't aware of it before).
Snogging.
You are using a false frame of reference.
Yep, it would be stupid to send someone with a fear of flying off in turbulent conditions for a 2 hour flight - the damage could be severe.
BUT, a 15 minute circuit on a calm summer evening is a whole different matter, PROVIDED the person involved is not coerced and can always stop the sortie quickly.
When I owned a plane, I used to do these sort of little flights every now and then and generally the passengers said it heldped them a lot. Usually they had control for a few mintues too, although not always.
However, it isn't a panacea for all and shoudl not be forced on people.