The opinion you entertain so completely that you functionally believe it while you express it, no matter the possibility that you will express-and, to an extent, believe-an opposite opinion later.
John was telling Kate to "just accept that women in video games have huge breasts because that's what sells and we should let the free market function as it will". But that appears to have been a stanislavski opinion, because two days later he was arguing that the writers for Star Wars should focus on it's "real fans" rather then diversifying the cast "Just to sell to a larger audience".
Someone who is addicted to obtaining money and building wealth. A money addict and fanatic. Breadheads often work more than one full-time job, and some even participate in illicit activities to "obtain the bread".