As a commuter who has been coping (until very recently) with the Compstall Road traffic jam for the past twenty years or so, I have a lot of sympathy with those who oppose further housing in that area.
But what's the alternative? Certainly not restoring it as a 'Styal Mill' type visitor attraction - given the colossal upfront restoration costs, followed by the high running costs, anyone who suggests that this could 'bring in revenue for the local council' really is in la-la land!

Just ask the National Trust.....
The fact is that there is a shortage of housing. Planning restrictions on green belt land mean that suitable sites are extremely difficult to find. 'Brownfield' sites such as former mill buildings are therefore preferred. People have got to live somewhere. It's as simple as that.
The way to tackle traffic congestion is by improving public transport, not by leaving people homeless.