The Sinners alongside Charlie are at the top of the foodchain in Hell, as they are being protected. In HB, there is no one protecting the characters. It's the bottom of the rung, and so lends itself naturally to darker stuff.

The lack of law or police makes things easier for them. Imps, on the other hand, get crushed, exploited, and abused by everyone and they have no way to defend themselves.

For a lot of Sinners, Hell is a form of freedom to them; just look at Cherri Bomb and Pentious being free to blow things up all day long. Angel has easy access to whatever drugs he wants (when not at the hotel), and Alastor can go around killing whoever he wants to.

I think part of the reason for that is that Sinners have privileges that imps don't get. They have rights, they have power in numbers, they get a voice, and have the Princess of Hell herself advocating for them. Imps have none of that, and so their trauma is more raw and deepset.

I've been wondering this since 'Oops'. It all seems very personal to him. There also happens to be a snake Goetia that we see in the background during Mastermind.