Jump Down Someone's Throat(become angry with someone)
That's it, Greg! You'd better not come in after midnight again tonight!
I know, dad. You don't have to jump down my throat! I told you that I'd make it home around 11:30. I don't intend to be late!
Well, you've said that before and in you come at 2:30 in the morning. You can't blame me for getting angry and scolding you. I've got good reason.
You'd better > It might be better > It would be better
and in you come = and yet you still come in
good reason = 十分な理由