She is saying that the "open web" Mozilla envisions is one where Mitchell Baker and her friends get to censor and manipulate content directly in the browser.
Obviously, people of the same ideology as her will agree with that, because they hate openness and debate. This is an excellent reason to stay away from Firefox. Using it is getting very close to being a political statement, which given the blog post, could mark its users as those in favour of in-browser political censorship.
Edit: very strange that some people cannot see this. She is extremely explicit:
> Donald Trump is certainly not the first politician to exploit the architecture of the internet [...] to foment violence and hate, and reinforce white supremacy [...] and he won't be the last [...] changing these dangerous dynamics requires more than just the temporary silencing or permanent removal of bad actors
Let's rephrase that: she claims the "architecture of the internet" - that's the web - has "dangerous dynamics" because (she thinks) it helped a Republican. Not some specific website, or some specific incident, or even some specific politician! The whole design of the internet itself is dangerous, and hence she demands "solutions" to make a "better internet" that goes beyond mere "permanent removal of bad actors" but rather solves the problem pre-emptively before "untold damage is done". Nobody who runs a browser should have this kind of revulsion towards what the internet is.
The only point in this piece that sounds like that is “Turn on by default the tools to amplify factual voices over disinformation”. It’s fair to disagree with her on that point but also consider that in conjunction with her call to make feed algorithms transparent. So she is saying to give preference to NYT over Breitbart by default but also make it obvious that is what you are doing.