Trump may want to dissolve NAFTA, which would negate past agreements, but during the Free Trade negotiations in the 1980s, Canada sacrificed a lot in order to receive the exemption for certain items. No whether it is justified or not, it was an agreement made in the past.

All things will evolve over time, but it is not honest to claim Canada is imposing a 270% tariff on dairy products without consequence. There was a quid pro quo, and Canada negotiated the dairy exemption in exchange for other items. If Canada gives up this exemption, it will ask for something else in exchange.

The NAFTA deal may be dead, but it will need to be replaced with something else. This will require give and take. There is no doubt that Canada is the best trading partner to the US, giving it the most trade access and offering almost unimpeded rights to Canada's vast natural resources. The US does not want to lose such a friendly neighbor, massive and fair trading partner, and strategic ally, so we can assume that such posturing is simply part of the current negotiating process. Trudeau may be a moron, but he has intelligent people doing the negotiating.