The Bronyetiquette tumblr is pretty much the antithesis of Niggertron. It churns out poorly though-out macros on how to be a good brony. As I understand, its been around since Ponibooru , and naturally, it shows up on Derpibooru too.  
They want what all moralfags want: everyone stop saying nigger, stop saying retard, stop offending everyone and everything. Their approach is understandable, but flawed. The ideas in each macro are reasonable and often downright obvious. The trouble is that these ideas come across as explicit commands with an air of moral superiority. This does nothing to change bigotry in people, and just aggravates people who would otherwise agree with such sentiments.  
To truly change peoples ideas, it is better to lead by example. People will emulate a role model whom they respect. People will not emulate a quickly-made image with text.  
Besides, anyone who takes this shit too seriously is just asking for trouble. There wouldnt be half as much bigotry within the brony community, or the internet in general if it werent so damn fun.  
Niggas aint gon change. Just deal.