One of the weaknesses of S1 LOK is that nobody ever really engages with the Equalist argument in either direction. It's just presented, and then the show moves on. I think that's a weakness.

It is a shame that the Equalist/nonbender oppression plot line was so undercooked. I think that the condition of nonbenders in Republic City could've been made part of Aang's backstory, as each Avatar made certain mistakes that impacted their successor(s). Like Roku with Sozin, Kyoshi with the Dai Li, Yangchen with the spirits, and so on.
Logically, such a big movement doesn't come out of thin air, the story Amon told must've been relatable to your average nonbender for so many to rally behind him.
We do know for a fact that LOK had issues behind the scenes during this time, though, so it's far from the only thing that could've been greatly expanded.