Maybe he blames Guardians for Mara’s “death” and the Reef’s struggles? The Reef Wars against the House of Wolves were to stop the Wolves from joining Twilight Gap and to protect the City. The Reef did all that to help us, and we didn’t return the favor until decades later in HOW, and that was just one Guardian. In the battle against Oryx, the Reef lost its Queen and most of its fleet to stop Oryx’s advance and give the City time to plan an attack. Again, the Awoken made a sacrifice to help the City and Uldren had every right to assume that we did nothing in return.