In my personal experience, I rarely even noticed the dislike count. Sometimes I'd wonder who the few unfortunate people were who disliked a video with about 1000x as many likes. It reminded me of the 1 star reviews you see on Amazon complaining about the postman for a product that otherwise has a stellar record. I just assume something is wrong with those peoples computers which made their video glitch out or something. I don't really trust negative feedback that much when it is paired with an overwhelming amount of positive feedback for the same thing. And I don't think I ever encountered a video with anywhere near the number of dislikes as likes, let alone more dislikes. I personally have never disliked a video. If I'm watching something new, I'll just watch part of the video myself, and decide if I want to watch the rest or click away to something else.
When I heard the announcement of removing the count as an effort to combat brigading, it made a lot of sense to me. I've seen the growth of negativity across the internet in the last few years. People are actually addicted to outrage these days, so anything that can help eliminate that seems like a good idea to me. The fact they kept the button there and still show the count to the uploader seems like they've at least tried to appease the diehards who appreciate having that dislike button - pretty fair if you ask me.
You may challenge the assumption that only diehards care about this, but I've just looked at a few videos in my feed to see the number of likes and it's abysmal. 40k likes for a video with 4M views. 18k likes for a video with 800k views. They're all like that. The like/dislike metric just doesn't have much engagement. While you predict dire consequences for YouTubes future and panic among their employees, I am thinking that casual users probably have not even noticed at all.