A simple affirmation would have been a sufficient response to the question Rodolphus had asked, but Snape could not let the issue rest so easily. "It's impossible to play any other part. Dumbledore's trust is an asset that I would dispose of only after it had served it's purpose to the fullest. And so long as I have his trust, I can't turn a blind eye to the insight it offers." Snape's words were open to interpretation, but no level of scrutiny could wrestle any hints from his cold expression. To imply that his involvement in the Renegades was indispensable was insubordination that bordered on an outright challenge to Rodolphus's authority. Snape was sure that Rodolphus would realize this. The question was how he would react to such a statement. The answer was sure to be a telling one...
"Is it so surprising? The self-righteous will adhere to any cause. Dumbledore doesn't care what he is defending, so long as he's the one orchestrating the defense."