I watched that with interest as Honister/Buttermere isn't far from where I grew up. It was a difficult (and moving) watch at times, knowing what was going to happen...
Instinctively, on the basic headline fact that he wanted to install a zipwire from the top of an isolated fell, I'd have been against the plan; but when you look at where it was proposed to be installed - like you say, SRD - in a post-industrial landscape, starting from near a mine workings exit and dropping to a mine/quarry building along the route of an old quarry winch line (if I understood that right), I thought it looked like a fine idea. I struggled with Friends of the Lake District's argument that this would destroy the peace and solitude on this one fell, given that there's a bloody great mine and quarrying operation off the side of it (and at the top of Honister pass, not hidden away in a valley somewhere).
A deeper look at the post-industrial point would have been good. A huge amount of the Lake District is post-industrial - slate, copper, lead, iron, graphite mines, charcoal burners - and it would pretty quickly boil down to differing views of at what point do you freeze man's impact on the landscape.
But then, Mark Weir had been pretty cavalier and no doubt rubbed a lot of people up the wrong way. I didn't know the via ferrata had been closed (disappointed, as well, as I'd always quite fancied giving it a go), but it doesn't take a genius to know what's likely to happen when you stick it through a SSSI. Wouldn't surprise me if there was a bit of settling of scores going on as well.