[Adam]

Here's your proverbial "when in Rome" moment. This is going to vary by who runs your organization and their philosophy. Some will tell you to call the foul, regardless. I know for a fact that some evaluators will tell you to use the old "force out" call here and give the ball back to A without calling the foul.

Pragmatically, I can see the basis either way. If you call the foul, B loses their best player; but if you don't call the foul, B's best player is going to do it again and you'll have to deal with it.

Personally, I would say call the foul. If B1 has four fouls this early in the game, he's not playing good defense anyway. It's much easier to justify the foul by rule. But there are good officials I know who would tell you to go with the "force out" call.