Different context:
But sometimes socking someone consistently annoying is sooo gratifying. :)

Depends on the circumstances so I say the statement is incorrect. In the case of self defense, the use of force (violence) may be justified. Not initiating force may result in the loss of your own life or the life of a family member. It is a judgement call.

What if B unholstered his weapon and A continued his threats? Would B be justified in shooting?

?????
John Galt's speech was sure as hell justified.

“Violence” is defined in the Webster’s New World College Dictionary, 4th Edition as “1. physical force used to injure, damage, or destroy; extreme roughness of action.” A threat is not “physical force”.

Clearly, it is B. A could have just run away.

So Ayn Rand should have added "unless justified" to Galt's statement?

Do you think that Ayn Rand had a clear definition when she wrote "...no man may initiate—do you hear me? no man may start—the use of physical force against others..." Remember she had Dagny shooting a guard who had not initiated violence against her?

If A is twice as big as B and B for limping can't run away like concealed carry me, B just may consider his life in danger.
Other possible variations A and Bare countless, though.

Dependeds upon your definition of initialing violence. If I walk u and hit you in the face, that's wrong. If you are walking toward me with a knif yelling I'm going to get you. If at all possible I'll hit you first and as violently as possible if I can't get away.
Question is who initiated the violence?
It is never cut and dried or simple to allply as saying initialing violence is always wrong..

I know I'm picking examples that really stretch you statement but just trying to show that a clearer definition of initiating is needed.

If A threatens to punch B in the face and B responds by shooting A, which one has initiated violence?