It wasn't just Diefenbaker - the other Canadian armed forces also campaigned against it - presumably on the grounds it would eat the whole defence budget. Looking back you have to ask was there any chance that other countries would buy it - or buy it in significant enough quantities to bring down the unit cost?
It might have made it if it was built in the USA or France but I can't see anyone else being willing to back such a programme. The UK did the same with the TSR-2 a few years later of course