^I don’t support building the layover yard there, but this does seem to be a case of overplaying one’s hand with questionable arguments.
In no universe will the Don Valley ever be a pristine nature preserve.
The Don needs to be developed carefully and with restraint, to minimise the impacts of necessary transportation infrastructure and to optimise its value as parkland against other uses..
In my eyes the layover yard is inappropriate, but the railway line has potential value as a future rail corridor, and needs to be retained as such.
- Paul