Well, it is presumptuous of a servant to do something like that, but...
[If Ciel insists.]
We are the kind of people to commit acts considered cruel, are we not? And likewise the kind to enjoy the feeling of kicking others. And we are both committed to seeing the young master's goals through?
[Marvel at how bad Sebastian feels about presumptuously having to compare himself to Ciel. That's why he's picking the nicest things to say, obviously.
The chocolate level lowers somewhat. But only somewhat, because, really? Those were obvious enough he might just as well have said "we both have two legs".]