At first glance, Red Hood's words seemed unobjectionable, and they even gave Damian a way out. But Thomas, Martha, and Bruce all frowned at the same time because they had realized that the original Bat-family's social education was even more lacking than they had imagined.
Damian demanding Nightwing's seat was more like a comprehensive challenge to authority. First, Nightwing was older than him. Second, Nightwing was already the leader of the group of outsiders. Third, Nightwing took on more responsibility for caring for others in this family than Damian did. Who sat down first was actually the least important part.
That meant Damian and Red Hood had absolutely no idea what was happening in the room. They did not understand normal social rules, social cues, or even the emotions others were expressing.
Anyone who encountered the kind of person who only made demands without paying any price, vented their emotions regardless of the situation, and believed everyone should indulge them and do as they wished would probably feel overwhelmed.
Most of the time, such people were not malicious. They simply lacked social education and did not know how to find their place or influence others in a group rationally. So they could only vent their emotions, making them seem like they were throwing tantrums.
Damian actually felt that he should sit closer to Thomas because he believed he was closer to Thomas. But he had no idea how to use that reason to persuade others, so he could only make demands or come up with clumsy excuses that sounded absurd.
Nightwing had barely spent a few days at the manor before, and it was the younger Dick, not him, who was close to Aisha. Yet Damian casually came up with a completely baseless reason without any hesitation, even firmly believing