@sistheren
dont know if that explanation works for you but anyway:
would he be a arrogant young black dragon as described by older ones otherwise?
and he is a dragon and humans are a lower race and all that jazz...
thats a trope that exists since 1990's even tenchi muyo included a racist alien king that discriminated against earthlings only to be chastised by his earthling wife
also to aiden that gramps was pretty much just a surrogate or a proxy he arranged for until he finished his growth so tolerating that grandpa interfering because he noticed how much that "tool" means to his treasure actualy shows how much he is trying for her sake...
its not like humans can change their ways over night so why should a lizard that can live about 10-100 times as long be able to?
important thing for me is that he keeps trying and shows gradually more restraint like how he didnt just smash that barrier and went after her to ruin the meeting
which tbh is something the aiden from the dragonheart incident would have done without a second though
edit:
excuses and explanations are two different things in my book excuses are ment to forgive something and an explanation is the underlying reason for a action or reaction and this is ment to be an explanation not an excuse but this edit could very well be counted as an excuse