Nah, this is more logical than the traditional situation where mysteriously people with special powers are living two lives, and few in the society have any idea such powers even exist. I mean, the setting of this series assumes those people have been around for ages, so it makes a lot more sense everybody knows about them than very few.
Why they are just let to run around destroying things, however, is more likely just a solution to allow nice fights. There is, after all, also the special police division apparently observing the supernatural occurrences, but they can do little about them, themselves. Or perhaps they could with tanks and attack helicopters, but those would produce even more collateral damage...
Edit:
Episode 7 v2 - AniYoshi
Hmm... After this episode, I might understand a little better what you meant. The girl basically mass murdered who knows how many people, and didn't get punished at all. Well, you could say that's somewhat dodgy logic, even if the society didn't control how much those magical clans fight among each other. But this time it was ordinary people getting slaughtered.
Or perhaps Kazuma lied to the police and told the boy had killed the people and Misao had just been a victim in a plot. Considering Kazuma's personality, he could have done such a thing without a second thought.
Edit2: Changed the episode link to version 2.