Animal Liberation and Reason in Ethics

I think to answer that we have to get into a discussion about the nature of rationality and reason in ethics. It seems as though although it might be unfair or ethically unsound it's perfectly rational for somebody to care about their own interests more so than those who are not close to them. In writing animal liberation I wasn't really trying to challenge that view but was building on what David Hume had said which is that essentially reason always starts from some desire or concern. So if as most people do you have most concern about your own interests then there's nothing more to be said against that being a rational thing to do.