His point was about requiring a login on another social network to vote on a video, when you're already logged in to Youtube.

You somehow boiled it down to a discussion on the lack of a "thumbs down" button. I think you're off track here. YMMV.

What "other social network"? Google, + ,and YouTube accounts are on their way to becoming one (if they aren't already).

Google doesn't care what info you put in when you sign up for a "normal" account, they just use it to correlate interests for ads and recommendations on the site. But to sign up for Google+ you have to use your real name or risk being banned.

Google+ and Youtube have always been mentally separated.

I could like videos on Youtube without the risk of them appearing anywhere or being used for anything. This has changed. And frankly it sucks.