Again, I'll take the first stab at answering that question.
I think it's important to understand that the fundamental way in which the international tax system works is effectively comity, which is an international principle to the effect that we do what we want here and foreign countries do what they want to do in their own jurisdiction. When we mix up notions of avoidance and evasion and low tax rates, I think we're missing the fundamental point, which is that it's the right of the sovereign country where the income is earned to maintain its own tax system and to determine what its tax rate should be.
If in Canada we chose to cut corporate tax to let's say 25%, how would we feel if a foreign country intervened and said “That rate is too low, so we're going to jack it up”?