We are complex, and to generalize on such a basic level does not and cannot fully encompass our species.
Gregersen's second point is also based heavily on the readings of Cicero. He writes, that to be human is to be "a rational being" (8) and exercise judgment in decision making opportunities. An example of this is our common choice between right and wrong. Daily we all make split second decisions regarding right versus wrong and it is most definitely a characteristic we possess as humans, however this is not a distinction we can hold alone. If you look at a trained dog, they have learned that eliminating indoors is not an acceptable behavior. In the same way humans are brought up and taught right from wrong, dogs and other animals can be taught as well. Therefore this reason is not specific enough to be included in our definition of the human.
Third, Gregersen writes about morality. To be human is to be "accountable for [your] deeds" (8). Again I see strong evidence to defend this statement; I see humans pleading guilty in court rooms and accepting responsibility for their actions. I see humans mourning the loss of loved ones and exercising proper morals in this time of hardship. Yet humans are not the only species to show an understanding of morals. Elephants, for example, also mourn the loss of a family member, and as a result on these grounds we cannot separate humans from elephants and cannot define humans as being "accountable for [our] deeds.".
Next, Gregersen explains that humans can be classified by our ability to possess different identities and unique character. It is true that each human has a different role in society and has a unique character; however we are not alone in this practice. The clearest evidence against this can be found in any pack animal. Within a pack of animals, regardless of species there is an alpha male or female. The alpha leader serves a unique role and manifests unique characteristics to obtain this position.