At the time the episode aired, it was in fact true that traders were not legally required to act in the client's best interest. Since then, though, laws have been passed requiring this for certain types of accounts (and further laws are coming, closing more loopholes).
Brian Klugman (Oliver) is Jack Klugman's great nephew. Jack Klugman famously played the titular character on Quincy M.E. (1976), who also used forensics to solve crimes.
Banging telephones when a deal falls through or a client is lost is quite common among hedge fund traders and other traders who work in bull pens, which are quite testosterone-fueled. In fact, *not* being violent with the phone can be seen as being "wimpy."