So to explain things to those still confused:
1. The family treated the A-rank with kindness even after his initial transgression because of the difference in status. While they likely know that Dariel is stronger, they would still have to observe some level of decorum to uphold the relationship between public and guild. The A-rank, meanwhile, believes that the Hero is the only one worth paying attention to there, and treats everyone else as if they're a second thought, as he typically would anywhere else.
2. A-rank's attitude changed so swiftly because he realized, in order, that:
- Dariel is absurdly powerful, enough to perfectly replicate the previous Hero's signature move better than himself
- He just pissed in Dariel's cheerios by destroying his house and disrespecting his family
- He's put himself in a position where he just attempted murder in front of someone who's powerful enough to hold him to whatever consequences he wishes, legal or otherwise
3. Dariel tried to resolve things quietly and peacefully because he very specifically doesn't want to disrupt the peace of his home town by involving a large entity like the guild. If he were to press charges OR off the guy for his crimes, he'd inevitably wind up caught up in some massive investigation and probably roped into helping the Hero anyways to "atone" for his perceived offenses against an adventurer of prestige. He just wants these people out of his hair as quickly as possible so they can get back to their slow daily lives.
So what it really boils down to is a difference in the character's priorities and prior knowledge, along with an unspoken understanding of social hierarchy typical to these fantasy settings. The author tends to move things too quickly for ideas like these to be properly explained. They seem to rely on an assumption of readers picking up on these things from other similar manga. Perhaps not a terrible assumption to make, but rather stick to "better safe than sorry" in these cases. Assumptions usually wind up burning you in one way or another.