'Licence to discriminate': US watching same-sex wedding cake Supreme Court case closely, page-2

in australia, to my knowledge, in your business you have the choice to enter a "contract" with who ever you want and whoever you don't want

i recall in a law subject i did asking the lecturer about this, the answer was along the lines of...

e.g when you go to a milk bar and buy a loaf of bread for $2 you simply give the cashier $2 and you have entered a contract to exchange money for bread, even though no words or documents were written, and the "contract" stands. also was noted that if someone gives you $2 for the bread you have the right to refuse the contract and say 'no im not selling you that item'

so if this were to happen in australia would it not imply - if my lecturer was correct - that any baker, wedding related entity can refuse to do business with gays?

con someone critique me if im wrong