The activists are the leaders of the Italian "Anti-Vivisection League."
The League that has exhorted Pope Benedict XVI in this matter has long debated with Catholicism in Italy.
In particular, AVL members employ a philosophy that, in order to highlight the so-called “rights” of animals, minimizes the actual rights of human beings, especially those humans who are the weakest: the comatose, the handicapped, the elderly, children, the unborn.
Among the “inspirations” and sources of AVL thought, one finds dependence on the writings of Peter Singer, also an animal activist, who actually proposed the killing of children born with deformities. In “Practical Ethics,” Singer says that "to kill a newborn with malformations is not the same as killing a person and, very often, it is not even an error."
Singer holds the same in regard to those who have suffered irreversible brain damage, or who are comatose:
"their lives are deprived of intrinsic value."
Peter Singer declares:
"the doctrine of the sacredness of life is a product of Christianity. Perhaps the time has arrived to think of these questions (abortion, infanticide) beyond the framework of Christianity."
The Anti-Vivisection League has issued their statement on their website, www.infolav.org, which is in Italian.
You can read about the Anti-Vivisection League's exhortation to the Pope in an English article about the event.