From what I can tell, Iceweasel is more or less a reskinned Firefox: there's some code changes to make it compatible with Debian's licensing guidelines, but it would be reasonable (in my opinion) to describe Iceweasel as 'Firefox for Debian'. And so are you also certain that the maintainers of Firefox comply with your requirements?

EDIT: Seems like they edited their comment instead of replying (kinda weird?), answering "yes" to my question. Perhaps I am a pessimist but I am doubtful that every single maintainer involved in Iceweasel complies with their requirements. And presumably this applies to more than just the browser: what OS are they using? What apps do they use? What phone do they have? What bank do they use? What car do they own? Etc. When you take such a hard stance against something over a refused pronoun PR (which btw was definitely chuddy of him), you nonetheless invite scrutiny against yourself, particularly when you say things like "You might be amoral, some of us give a fsck."

What I'm assuming is that 1attice is boycotting public statements, not actual impact. It's why JK Rowling is so hated but not Orson Scott Card: the latter is likely giving just as money money to objectionable causes but he's not being loud about it [anymore], whereas JK Rowling is being loud... very loud. And so buying Harry Potter merch becomes a litmus test for morality, but not buying Ender's Game merch. Alas.