"The Mr. Robot Malware?" You mean the extension that did literally nothing unless you turned it on in about:config? That's "malware?"
Mischievous easter eggs don't really belong in commercial software anymore (with very careful exception) but the allure still exists. I can't fault the dev team too harshly for this lapse of judgement, especially since it sounds from their blog post that they've taken the backlash to heart.
It was just weird and it freaked me out until I heard everyone else was losing their mind over it. I just really don't get what they were thinking.