“Humanitarianism is the name commonly given to that higher humanity which embraces the whole animal kingdom, or as much of it as gives evidence of feeling. Humanitarianism is the final goal of human sympathy. Starting with the tribe (or the family, or even the individual), the instinct of sympathy has spread from tribe to confederacy, from confederacy to nation, from nation to race, and from race to species. It is constantly growing and deepening among the sub-divisions of the human species and is as constantly extending to the non-human populations of the earth. It is destined finally to reach the remotest shores of the Great Ocean of Feeling. Wherever there are bodies that bleed and souls that mourn, there human sympathy should go, angel-like, with its sweetness and healing down even to those lowly and overlooked but suffering-and-enjoying civilizations beneath our feet, in the grasses and grounds and the crystal deeps.”

The fact that an animal is a human, that is, that he belongs to the hominine species of beings, entitles him, regardless of his imperfections, to some sort of consideration.
Source: Better-World Philosophy: A Sociological Synthesis (1899), The Social Ideal, p. 143

Epilogue
Raising the Peaceable Kingdom (2005)

Species Conservation in Managed Habitats: The Myth of Pristine Nature (2016), p. 51

Source: Every Living Creature (1899), p. 30

volume I, chapter III: "Comparison of the Mental Powers of Man and the Lower Animals — continued", pages 100-101 http://darwin-online.org.uk/content/frameset?pageseq=113&itemID=F937.1&viewtype=image
The Descent of Man (1871)

"Take Heed that Ye Love not Human Glory in any Respect," A Select Library of Nicene and Post-Nicene Fathers, vol. 11, p. 66

Transhumanism (1957)
Context: We shall start from new premises. … The human species can, if it wishes, transcend itself — not just sporadically, an individual here in one way, an individual there in another way, but in its entirety, as humanity. We need a name for this new belief. Perhaps transhumanism will serve: man remaining man, but transcending himself, by realizing new possibilities of and for his human nature.
"I believe in transhumanism": once there are enough people who can truly say that, the human species will be on the threshold of a new kind of existence, as different from ours as ours is from that of Pekin man. It will at last be consciously fulfilling its real destiny.

Aphorism 41
Novum Organum (1620), Book I
Context: The Idols of Tribe have their foundation in human nature itself, and in the tribe or race of men. For it is a false assertion that the sense of man is the measure of things. On the contrary, all perceptions as well of the sense as of the mind are according to the measure of the individual and not according to the measure of the universe. And the human understanding is like a false mirror, which, receiving rays irregularly, distorts and discolors the nature of things by mingling its own nature with it.

The World's Religions (1991)
Context: The religions begin by assuring us that if we could see the full picture we would find it more integrated than we would normally suppose. Life gives us no view of the whole. [... ] It is as if life were a great tapestry, which we face from its wrong side. This gives it the appearance of a maze of knots and threads, which for the most part appear chaotic.
From a purely human standpoint the wisdom traditions are the species' most prolonged and serious attempts to infer from the maze on this side of the tapestry the pattern which, on its right side, gives meaning to the whole. As the beauty and harmony of the design derive from the way its parts are related, the design confers on these parts a significance that we, seeing only scraps of the design, do not normally perceive.