Agreed i was pissed off when they started injecting politics into my browser recently.
Mozilla has always been political. It was born so. Why do you think Jamie Zawinski got Shepard Fairey to design its logo? The Mozilla manifesto is full of political statements. Do you remember the fight against DRM? Net neutrality? SOPA?
Often, people that speak like you mean “speech favoring equal treatment” instead of “politics”.
https://www.jwz.org/blog/2016/10/they-live-and-the-secret-hi...
Furthermore Mozilla has the expertise, connections and brand when it comes to the web they can use as leverage to solve web-related social/political issues, but might not have much leverage for unrelated issues so the risk/reward ratio will not be in their favor.
If I keep that in mind while listening/reading people complaining about "politics" it is often the smallest change to their stated message that would make it clear and internally consistent. So I ask clarifying questions to see if their complaint is poorly articulated rather than picking at their words to defend the thing they're criticizing.