Opponents of a minimum wage need only believe that increasing the price of a thing tends to proportionally decrease the demand for that thing. This is simply a statement of the law of supply and demand, which is (though weaker) the economic equivalent of physics' F=MA. Proponents of a minimum wage need to believe that in this particular case, raising a price does not proportionally decrease demand. While this may be…
No, it's a contradiction of it; in conventional economics, a price floor has no effect on supply or demand, but reduces quantity traded iff the market clearing price without the floor is below the price floor. (One of the most annoying recurring things, to me, on HN is people making economic arguments and confusing either “supply” or “demand” with “quantity traded”, especially when discussing the effect of price controls which result in quantity traded not being the intersection of the supply and demand curves.)