The position and the execution of its duties is supposed to be impartial and non-partisan. There is no requirement at all that this also apply to the person elected or appointed to it. Few positions in government would be filled at all, if that were the case. We know the political affiliations of just about every judge on the federal bench, for instance.

In this case the partisan cause is likely "have as many people be able to vote as possible". This is partisan because most people who get unintentionally disenfranchised are Democrats but the increase to franchise definitely does serve our Republic

For starters, he didn't actually say that. He said:

"This actually will be a great way for me to be more involved in my neighborhood and work actively toward more progressive change. I actually have a background in community organizing, and while I'm not entirely sure how this position could align with that, it seems like an opportunity to find some ways to at least more deeply connect with my neighbors."

He's talking about becoming more active in his community on a personal level.

Given that he states he's instituting Taco Tuesday as one of his first acts, I'd suspect people are getting the vapors over a trivial joking statement.

I'd also imagine the powers of an election judge are pretty limited. It sounds like they're the Philly equivalent of the person who runs an individual polling place in NY. Not much wiggle room for causes of any sort.