The antagonist of the SE5 premiere sought to make everyone "equal" and took their cutie marks and replaced them with an = sign.

One point in the episode, the "=" ponies asked the main characters how they could be friends while holding different opinions.
Ponies that broke the rules in equality town got thrown in jail and had loudspeakers shouting "equality" propaganda at them.

The antagonist, however, had not actually given up her cutie mark (talents) and was just covering it. When the town found out they turned against her and took their cutie marks back.

The moral was that forcing everyone to be equal wasnt equality, and that you dont need to hold all the same opinions as your friends.

The reason SJWs are compared to the antagonist is that she was operating a system similar to communism or fascism, and SJWs are compared to these systems frequently. That and the symbol the ponies were rallied under was an = sign.
If you're willing to sit through an episode of MLP. You'll see the resemblance.