halacha - Count someone in a minyan or embarrass them?

Theoretical question. Yankel is a born Jew, and he marries a giyores, Shprintze. The two of them live a happy life together, and Shprintze eventually gives birth to a son, Berel.

Decades go by. Eventually, something comes up that nobody had noticed before that makes Shprintze's conversion invalid. (Let's assume, for the sake of the question, that her conversion is actually invalid, and not just out of doubt.) She and Berel plan to convert once again the following week.

Reuven eats over at Yankel's house Shabbos day, and Yankel, being very close with Reuven, decides to reveal this piece of information, trusting him to keep it a secret. (Please don't ask about any questions of how Reuven may have violated some piece of Halacha by eating there. Just go with it.)

Shabbos afternoon comes. They've got eight guys for a minyan, including Reuven. Just before they give up at finding a minyan, in walks Yankel and Berel. Perfect! Ten guys for a minyan.

Except... Berel isn't Jewish. Everyone thinks he is.

Except for Reuven.

(Again, ignore the halachic issues that may surround a non-Jew being in a shul.)

The chazzan stands up to begin Ashrei. Yankel and Berel, for some reason oblivious to the problem they've just started, quietly take their seat in the back of the shteible and are making no effort to stop the minyan now in progress.

What should Reuven do?

• Should he allow the minyan to go on, causing the chazzan to say Kaddish and Kedushah without a minyan, as well as the Brachos Levatalos involved in repeating Shemoneh Esrei?


• Or should he stop him, thereby embarrassing Berel in front of everybody?


• If he asks Berel to step out, he's stopping the minyan, which will still cause embarrassment to Berel, albeit not as much as the previous option. Still, he will be put in the awkward situation of explaining his actions to the kehillah, which could still lead to the secret coming out.


• Or maybe he should pretend he needs the bathroom for long enough that the minyan disbands, which would possibly lead to his needing to lie about his whereabouts or else spill the beans.


• There is no option to find another tzenter; remember, they were struggling enough to find a ninth person until Yankel and Berel came along.