i think his question is about the "any lawful purpose" bit. and yes, self defense is another lawful purpose. people get hung up on the physical locations, like hunting, gun repair, or shooting range. but the truth is anywhere you go with your gun that is a legal place for you to posses it is considered a lawful purpose:
http://www.legislature.mi.gov/documents/publications/firearms.pdf
"(b) "Lawful purpose" includes the following:
(i) While en route to or from a hunting or target shooting area.
(ii) While transporting a pistol en route to or from his or her home or place of business and place of repair.
(iii) While moving goods from 1 place of abode or business to another place of abode or business.
(iv) While transporting a licensed pistol en route to or from a law enforcement agency or for the purpose of
having a law enforcement official take possession of the weapon.
(v) While en route to or from his or her abode or place of business and a gun show or places of purchase or
sale.
(vi) While en route to or from his or her abode to a public shooting facility or public land where discharge
of firearms is permitted by law, rule, regulation, or local ordinance.
(vii) While en route to or from his or her abode to a private property location where the pistol is to be used
as is permitted by law, rule, regulation, or local ordinance."
just because it says "includes the following" does not exclude other activities