♫ She's the mare who's the talk of the town with the restless gun don't shoot broad out to fool her around keeps the varmints on the run, boy keeps the varmints on the run She's the top of the West always cool, she's the best she keeps alive with his colt 45. ♫
Wait, let me summary it better: Earth ponies can't fly/walk on the clouds(no wings) and don't have supernatural powers(no horns). So yeah... I think, they would be treated worse than ponies of other races in XVIII/XIX century (in a parallel universe ). It's stupid, but look at the south states of USA - once again XVIII/XIX century - They enslaved people because they thought they were superior because of skin color.