It’s not about identity as much as it’s a very poor way to try to convince someone.
Don’t base your line of argument on a statement you know the other person will likely disagree with.
For example “You should play Pathfinder because DnD sucks”, holds no weight to people who don’t think that DnD sucks. In fact if they happen to like DnD, it undermines your argument, because if you disagree about DnD, aren’t you also likely to disagree about Pathfinder?
There’re a lot of privacy enthusiasts who seem to view privacy as a binary. So because Mozilla isn’t perfect, it’s as bad as can be.
They also commonly have little understanding of the underlying technology, law, business, etc., which I guess is why they can’t do any threat modeling. They’re just really scared of a nebulous threat they do not understand. Which I can sympathize with.
But privacy then becomes more about “staying pure” in some abstract sense, rather than about avoiding concrete threats.
(As a tip to those who want to do better, any real security starts with threat modeling. There is no such thing as perfect security, it’s always a tradeoff. So you must do threat modeling to make sure you’re putting your resources where they will make a difference.)