Equal

I have a headcanon that goes into depth on how Starlight Glimmer became a communist-like town mayor and wanted everypony to be equal.

In harsh childhood days, she was treated badly among others. She couldn't cast magic, and thus leads to why everypony treated her in a negative way. She tried and tried, but nothing happened from this. She wanted to get back at those ponies, and show how truly powerful she was once she knew how to use magic.

As time went by, she finally gained magic. But that wasn't until long after. Starlight, reminding herself to show those ponies what magic she's got, decided to get a town together. She found the ponies who treated her horribly, kept them in captivity, and eventually rid their cutie marks with the magic she had finally gotten. By studying a spell for years, she was able to do this "cutie un-marking" spell. For their punishment of treating her unfairly, she equalized them all, making them live in a town where everypony is equal. Any passerby's she had no mercy on, and equalized them too. Starlight wanted to show the world what a powerful pony she is.