Spheris felt that striking a nerve but quickly decided to think nothing of it. After all, he understood the Dean's sentiment.
It was a difference of perspective.
For Spheris, he'd had a different experience with the Royals and so was slightly leaning to the possibility that they would not just forget about him and we're being restrained by their parents.
For Smallbutter who had no idea about the relationship the team shared inside the Expanded Realm and probably despised the Royals, it came as no surprise that he would be leaning towards the idea that they cared little for a Heathian thief who stole the place kept for their equal.
Also, because of his bluntness, Smallbutter wasn't at all scared to say it. No sugarcoating. As bitter as the words could be, he said them if he believed them.