Percy could see that he had hurt Cass with his words, but they still needed to be said, and he would do it again if he had the chance. Some things were more important than sparing someone's feelings.
"Well done, Cass, although you've never understood that it wasn't about the sex per se, but the trust connected to it, and you-" Percy snorted. "You want me to believe that you went through all of this, lied so well and completely when you could have simply talked to me, but you've never lied with anything else. I'm a Gryffindor, Cass, not a Hufflepuff. It's not that easy. You can't say the words and everything goes back to normal. You can't expect me to believe you. In fact, you can't expect me to doubt every single thing you've ever said to me. For all I know, you were fucking people left and right, or worse you were telling people about us, because that's the one way for Lestrange to find out about us."
Percy rolled his eyes. "Half a chance? How can I? I wouldn't put myself at risk, but everyone in our community, our department. How can I talk to you about work and know that it doesn't go back to someone who will eventually tell to Lestrange? You might not even realise it, but the end result would be the same. Tell me, Cass, would you trust someone like you with every secret of the Auror Department? Because at the moment, I don't think I can."