It hurt him less to be used like that than he had expected. In fact, if it had been for anyone other's than Albus" sake, he would have been far less sympathetic - but for all he knows, there is something special about Albus that attracts characters like that. People who would do anything to be close to him. Hope and dream for years, as in Scorpius" case. Spy, lurk for an opportunity and then seize it, like Avery.