I agree that dealers tend to label for selling purposes.
My professor introduced outsider art to us by teaching us about the European Outsider artist.
http://www.huntfor.com/arthistory/C20th/artbrut.htm
"Outsider" is being used for many things today. We even have Outsider poetry. Poems about Rebels, Exiles, and Renegades.
Outsiders (poetry)
Edited by Laure-Anne Bosselaar
Foreword by Al Young
Milkweed Editions
From the book:
"Every Last One Of Us Is Someone Eslse's Outsider."
Poet and jazz musician Al Young plays the introductory notes for this anthology about living or thinking on the edge. This collection of poems is a powerful montage, a complex portrait of the ways in which a society is fractured. Written from beyond the pale by those who don't belong to a majority or dominant group, these poems enter the world of the homeless man on the street, the man that lives between two countries,..." and more.
As far as Outsider art is concern, I believe it to be, and belong to the mentally ill, and untrained.
AE