Firefox is significantly more trustworthy than Chrome (the outrage over Mozilla's occasional screw-ups exists because that behaviour is decidedly not the established norm for Mozilla whereas the same behaviour from Google surprises no-one).

The context in this thread was "Switch to Firefox. It prioritizes privacy, unlike Chrome". In other words, "Firefox is more privacy-focused than Chrome".

Piling on Mozilla for past screw-ups creates the impression that this statement is wrong and that both browsers are equally bad at privacy because neither of them is consistently perfect.

Even if the criticism is technically correct, piling it on like this creates a skewed impression that if you care about privacy you might as well use Chrome because even if you switch to Firefox your privacy will be invaded anyway.

This normalises the level of invasiveness of Chrome and equivocates its consistent and intentional behavior with a series of exceptional missteps.

In case you think "But I never mentioned Chrome", well, Chrome and Firefox were the only options in the original post so anything negative about Firefox implies a positive about Chrome and vice versa. If you wanted to call out specific behavior, either present an alternative (Brave? Ice Weasel?) or clarify that you're addressing the behavior categorically and not just that instance of it specifically.

If someone says "Don't use A. B is better because it doesn't do $thing" and then you respond by "I've seen B do $thing" that implies equivalence between A and B even if B did $thing only a few times out of carelessness whereas A intentionally does $thing all the time because its business model depends on it. It doesn't matter that you didn't mean it that way, it doesn't matter that it's true and it doesn't matter that this is a mistake on part of the audience. Humans are flawed and communication requires you to take those flaws into account -- unless you just want to express yourself.