There is no way of proving your point to someone whose income or position depends on believing the contrary.
Arguing - Arguments Quotes
Prepare your proof before you argue.
There is no arguing with one who denies first principles.
The greatest war is the war of the mouth
Never argue with a man who buys ink by the barrel. (about antagonizing newspaper editors)
Two men in a burning house must not stop to argue. (Ashanti)
The only thing a heated argument ever produced is coolness.
He opens the door with an ax.
Use soft words and hard arguments.
In argument similes are like songs in love; they describe much, but prove nothing.