Alexander (previously) argued that only time after becoming a permanent resident should be counted for citizenship, because it is only after becoming a permanent resident that a immigrant (a foreign national) becomes a permanent part of this country, by finally showing the intention to make Canada his/her permanent home.
You may or may not agree with his point, but what the minister has not addressed is the fact that, even as temporary residents, these people who have spent a considerable amount of time in Canada before becoming PRs, have contributed to the society, learned the values and culture of Canada, learned the Canadian ways of life, learned at least one of the official languages, paid considerable amount of income tax (and tuition in the case of former international students). The government keeps espousing better integration to the society, I actually believe that even time you spent as TRs would help you integrate better with the Canadian society and make you more 'Canadian'.
Alexander may be right that it is only after you have become PRs that you can finally fully materialize the intention to permanently settle in Canada, but I don't think his arguments would be good enough to support the position of complete elimination of pre-PR time credit for citizenship, because it basically means that whether you have spent 5, 10 or 0 years in Canada, your 'Canadian-ness' (and contribution to Canada) would reset to zero by the time you obtain PR status, and I think that would be absurd and contradictory to what they claim they're trying to achieve with Bill C-24.