This is a very good point. If we agree cognitive biases make our understanding of the world flawed, why should we assume that our moral intuitions aren't equally flawed? That assumption makes sense only if you actually equate morality with our moral intuitions. This isn't what I mean by the word "moral" at all—and as a matter of historical fact many behaviors I consider completely reprehensible were at one time or another widely considered to be perfectly acceptable.