OK, fair enough. What aout this from the FAQ:

http://www.brickboard.com/FAQ/700-900/BrakesABS.htm#BrakeFluidBleedingFlushingProceduresforCarswithABS

I don't have a green book for brakes, so I can't claim to have a Volvo source for this. I have seen many references to clamping off brake lines, especially when using a C-clamp to depress a brake caliper in order to prevent fluid from possibly contaminating the ABS unit. I've also seen references to using a clamp on the line to prevent fluid loss when changing the caliper. So I think your concerns about crushing the brake line are unfounded. In fact I've done this myself with no ill effects. These clamps are widely sold for this purpose, but I wouldn't use any clamp that doesn't have a wide clamping surface. As far as proving old brake fluid (that doesn't typically get changed in a brake bleeding, BTW) can screw up the ABS unit, well I don't really know how you could definitively prove that, since even dissasembly of a ruined ABS wouldn't prove it was caused by old fluid for sure. I guess you roll the dice and you take your chances.