There have been quite a few instances over the past few years of Mozilla demonstrating its left leaning politics:
* The Brendan Eich situation where his private contribution to a conservative cause impacted his employment
* Baker calling a former conservative employee's views "traumatic and damaging" in their obituary - https://blog.lizardwrangler.com/2018/08/07/in-memoriam-gerva...
* The removal of "meritocracy" from the governance document in the name of D&I - https://blog.mozilla.org/careers/words-matter-moving-beyond-...
* Promoting BLM and anti-racism content via Pocket and their homepage
* Replacing "master password" with "primary password" - https://support.mozilla.org/en-US/kb/primary-password-replac...
Agree with their positions or not, they are definitely alienating to some. Even if just delivering a great browser and getting people to use it is not their primary mission (and it's not directly if you've ever read the Mozilla Manifesto), it is the means by which they retain the ability pursue those goals.
Recall Michael Jordan's reason for staying away from politics, "Republicans buy sneakers too".