You are suspicious because a tech company - which maintains the second-most-used browser in the world - wants to be more inclusive, as in, make people feel more comfortable with their products and community? That's pretty sad.
You're misunderstanding the suspicion in a way that makes me think that you already have a preconception of my worldview, which, in this case, is entirely inaccurate. You're painting this in a "either you agree with their marketing campaign and identity politics or you're against inclusion" way, which is the type of gross remnant this marketing strategy creates -- thank you for responding with example behavior.
FWIW, IE is the second-most used browser; Firefox is becoming less relevant. Maybe this campaign is meant to counter their downward trend in popularity of consumer-software, but it seems like they want to go into content creation/ideology.
Any time any large company takes on a new emotional or social posture, there is legitimate concern that it's just pandering and manipulating for business motives not social ones, and has little to no actual value to the concerns of your supposition.
Also, Mozilla is a technology company, and the technology itself is mostly oblivious to social issues (unfamiliarity with UI metaphors being the most obvious barrier), so it comes across as a distraction in terms of effort, which is especially concerning to donors.
