Graves learned a long time ago that Grindelwald wouldn't rape him. Flirt with him and make him uncomfortable. Torture him if he tried to escape. But rape him, no. So, when post-film Graves is kidnapped, tortured, and raped by others, it's a relief when he hears the sound of Grindelwald's voice, berating his captors for daring to touch what is Grindelwald's, mingled with the screams of the people who tortured him.