Utilitarian lacks beauty and goodness because it can theoretically justify genocide and slavery. They may maximize overall happiness or preferences - particularly if it is the slavery of genocide of a minority ethnic group.
And utilitarianism is inconsistent because if you are one of the people being consigned to slavery or genocide, you would not continue to hold your utilitarian beliefs. A belief cannot be held rationally if it cannot be held consistently. Ethical beliefs can only be held consistently if they adhere to the Golden Rule.
But that only scratches the surface. There are many, many reasons to not be a utilitarian.
"The gist of the article contained these two themes: 1) The Catholic Church has no right to speak out on the stem cell debate; and 2) embryos are not persons and have no inherent right to exist."
Singer is just like everyone else: he has opinions. As we all know, opinions are like body parts. Everyone has them.
His claim to some ethical stratosphere is just so much bunk.