on the bit

Who's afraid of Virginia Woolf?から、昨日取り上げた場面の直後です。
GEORGEは渋々と客を迎えに玄関に向かいます。
GEORGE: [moves a little towards the door, smiling slightly]: All right, love ... whatever love wants. [Stops.] Just don't start on the bit, that's all.
MARTHA: The bit? The bit? What kind of language is that? What are you talking about?
GEORGE: The bit. Just don't start in on the bit.
MARTHA: You imitating one of your studets, for God's sake? What are you trying to do? WHAT BIT?
GEORGE: Just don't start in on the bit about the kid, that's all.
GEORGEが言う "don't start on the bit" の意味が分かりません。　私が分からないのとは意味が違うと思いますが、MARTHAも "the bit" が何を指しているのか分からない様子です。
"bit" は少しの何かに関係する色々な意味がありますが、上の状況に関係しそうなのは次の意味ではないかと思います。
・Macmillan Dictionary: a small part usually with spoken lines in a theatrical performance
・Infoplease Dictionary: a stereotypic or habitual set of behaviors, attitudes, or styles associated with an individual, role, situation, etc.: the whole Wall Street bit.
GEORGEはMARTHAに、息子の事を話題にするなと言いたいようです。