Let's just agree top disagree on your statement that 'you can't really question the need for that road'.
![Smile :)](./images/smilies/icon_smile.gif)
Like many other cities Glasgow went down the new road mania route to the great consequent damage of the fabric and life of the city - but that's a whole different (and very heated) topic for another discussion
On the appearance of properties in Glasgow in the 1960s and 1970s I'd urge caution on drawing conclusions from images. The entire city was in an ugly dirty mess by that time (the black filth of industry and pre smoke-control was still there, and the council's stewardship of the public realm was not as well developed then as now.) A while back I was taking some Canadians around the city centre and I could hardly find a single example of remaining stonework that could give even a little glimpse of just how bad the stonework of the city was at that time. Nearest impression one can give is to say 'forget lovely tinted red, pink or sandstone and just imaging mostly ingrained soot black with some bits of grey and even less bits of dirty brownish red'.
The grime and filth IMO is a bit like general poverty, the danger is that after we have got rid of it, people get blase and either forget or have no real life experience of just how bad things were, and can get again.
On quality and the blonde versus red sandstone. Most of the very top quality tenements, especially of the later Victorian period were indeed red or pink sandstone. A great many of the blonde sandstone tenements were, nevertheless, of top quality. I'm aware of a few red sandstone tenements that were of inferior quality. I suspect in some cases the builder was using some inferior red material (stuff that was cut out of the bed etc.) because he could get it cheaper and it added a bit of superficial quality to the appearance of the building.