They had driven away a lot of people who were recommending themselves to him.
It was almost becoming their main job because in almost every place that they would go, there would always be someone who was throwing themselves at him, whether it was women or men.
Dion was just one of the people who was attracted to Sir Treyton.
So Derek really doesn't like him because he was already acting out of line by driving away some of Sir Treyton's lovers in the past even though he wasn't even noticed by Sir Treyton.
Every time Sir Treyton picked a lover, Derek was always hoping that they had a better temper so that they wouldn't be the ones suffering from it.
Treyton had always instructed them to treat the lover he had as if it were his wife, so they had to be respectful to anyone that became Sir Treyton's lover.