"Something didn't just happen and I just didn't do anything." It was true, considering that the agreement was made in Severus' office. This was merely a verbal confirmation of previously stated terms. The choice of having so many people present was for him, Regulus knew that.
"He might not be happy, but he will include you, because it's in his best interest to have you there, no defections in the ranks. It's better for you, because you'll have the protection they can give you and you will be with your friends," he said. "No one needs to know about what happened with you and Dumbledore, and everything will be fine."
He smiled. "And I'm just that amazing. Even he can't resist me." He leaned in and brushed their lips together. "You don't have to protect me from him, and there are no machinations at play, just... a gentlemen's agreement."