I think the fixed gear craze has saved more classic bikes than it has destroyed. By renewing interest in old steel frames it must have saved thousands of frames from being thrown out.
As a classic bike rider rather than collector, the drivetrains of all my bikes are modified to either wide range doubles, single or triple chainwheels, hub gears, coaster brake .....or fixed gear.
A lot of fixed gear conversions are more respectful of the original bike than some high-handlebar conversions.
Tobit Linke, Dortmund Germany