Meanings of dangerous argument in English

That is a dangerous argument my dear Watson.

I should have thought this was a dangerous argument; obviously boys do learn better than men certain things.

He said: The idea that you can grow an economy on the back of rising house prices is a very, very dangerous argument.

There was little chance of making Saunders take the patent pill by persuasion-mainforce was a dangerous argument, and some thought claymores had edges.