I think that he is not greedy but silly. In such situation i wouldn`t agree cash out. You have to wait just 15 minutes, you team is winning - it is good chance. But i prefer to defend my bet. If he bet $100 against Sporting, he`ve got $100-150 profit at least i think. In the result it would be less, than he could get with cash out, but it would be nice profit without any risks.
He's silly and greedy actually (lol) maybe he's one of those who see cash out as settling for less or not been brave enough, meanwhile they fail to forget that you are getting an offer for a game of probability that the casino reserves the right to still withdraw such from you, so it's actunot a privilege you should feel was supposed to be exactly the way you wanted it and the way sports game are, anything can happen even within split seconds so why not grab an opportunity when you have one.