The following poem was written by a woman named Ella Wheeler Wilcox. She was writing around the turn of the 20th century, but her words clearly indicate that she was way beyond her time. 

So many gods, so many creeds, 
So many paths that wind and wind, 
While just the art of being kind 
Is all the sad world needs. 

I am the voice of the voiceless: 
Through me, their hearts shall speak; 
Till the deaf world's ear be made to hear 
The cry of the wordless weak. 

From lab, from cage and from forests,
From slaughterhouse stalls, come the wail
Of my tortured kin. They proclaim the sin
Of the mighty against the frail.

For love is the true religion, 
And love is the law sublime; 
And all that is wrought, where love is not 
Will die at the touch of time. 

Oh, shame on the mothers of mortals 
Who have not stopped to teach 
Of the sorrow that lies in an animal's eyes, 
The sorrow that has no speech. 

The same Power formed the sparrow 
That fashioned man - the King; 
The God of the whole gave a living soul 
To furred and to feathered thing. 

And I am my brother's keeper, 
And I will fight his fight; 
And speak the word for beast and bird 
Till the world shall set things right. 

Ella Wheeler Wilcox (1850–1919)

This is the most simple version, with slight edits for clarity. There are two other (longer) versions available online that are well worth checking out also: Voice_Of_The Voiceless