Whose responsibility is it to make a safe pass?

Situation –
Who
Racer A – A former National Champion on a Vintage bike
Racer B – A club level #1 plate holder who has competed in a few National events on a current 600

Time
Expert Practice

Racer A heading into T5 a double apex right hand turn
Racer B attempts to pass Racer A on the outside. Racer B slams the door on Racer A before he was clear. Racer B looses the front from the contact and crashes. Racer A remains upright and continues with practice. Racer B comes into the pits and begins to yell at Racer A.

What are your opinions?