Great topic.
Of course there are different views on this subject but when it really comes down to it, the owner has the right to do what he/she wants to do with their parts or machines.
The Purist is offended when vintage cars motorcycles or whatever are cannibalized.
The street-rodder, resto-modder, is trying to make a machine that is more drivable that a 50 + year old machine. And of course, a safer machine at road speeds of today.
A 50 + year old machine may be restored to exact original specs, at a high $$ cost, which is great. It may be driven a little, and showed as a historical piece. On the other hand the resto-modder is going to drive that machine. And maybe more people will see that machine, because it is able to be driven, like a new car.
Not everybody will be pleased.
If the resto-modder offers up some hard to find parts, that may allow the authentic restorer to finally get his/her machine finished.
Just recently I was able to get a restorer a very rare, actually non-obtainable part for a limited production motorcycle early 1930's, he was looking for this part for decades. That part only became available because of restoration could not be completed.
Some machines are destined to be donors, for others to survive.
intimeold