There is no doubt that Pierre Trudeau behaved terribly as a young man. In the context of the ultra-conservative catholic school environment of 1930's and 1940's french Quebec, he adopted the then in vogue views (amoung some but not all sectors of Quebec society), that supported Vichy France and was silent in the face of Nazi persecution of the Jews. The fair question that Brian Mulroney raises is did that behaviour as a young man render Trudeau morally unfit to serve as a leader of Canada.
In Trudeau's case we have the benefit of being able to look at the whole arc of his career and on the balance it seems that a misguided youth does not disqualify one from adult leadership. Indeed, the whole thrust of his adult life seems to have been a rebellion against that childhood and Catholic Quebec society. It is only in that light can his devotion to individual human rights and his use of the military in October Crisis be reconciled. We are not talking here about the actions of a Kurt Waldheim but instead ineffective, youthful rabble-rousing.
Trudeau and Mulroney are both remarkable in the manner in which they each effectively limited the scope of government in our day to day lives. Trudeau acted by introducing constitutional protection for individual human rights which has hugely limited the power of the executive and significantly limited the power of the legislature. A Maurice Duplessis, a wholesale repression of labour unions, day to day censorship or the banning of Indian potlaches are impossible to imagine in today's society -- largely because of Trudeau.
On the economic front Trudeau was a very different man. He believed in early, frequent and aggressive intervention, for example wage and price controls (which were also supported by Stanfield in the day). Mulroney brought an end to that era, mainly through the negotiation of the Free Trade Agreement, the dismantling of the National Energy Board and most limitations on foreign investment and the priviatization of many Crown corporations. As a result of this modern Canadian governments have a much more limited role in the management of the economy (and the Bank of Canada is the main tool)than would have been imagined in the 1970's.
This substantive legacy of both men is coming under critical examination today as a result of modern issues. Trudeau's indvidual rights reforms are under fire as governments struggle with (or take advantage of) the threat posed by terrorism. Free-ranging economic liberty is also being examined in the context of the rise of terrorism but more importantly in the context the global warming debate.
Rather than spending too much time looking at a dead man's childhood idiocy (which deserves to be condemned) perhaps we should be looking more seriously at the adult legacy of both these men. It is only by understanding the whys and whats of what they did that we will be well-equipped to have the debates we need to have in the modern conetxt.