Well funny enough, at that same time, Google blocked WP access to Google Maps, even through the browser. They claimed Google Maps only works properly in Webkit, even though it worked just fine in IE if you could get around their block. Couple that with the fact that, even after Google blocked WP's YouTube app, Google and Microsoft worked together to make a new app on HTML5 (proving wrong your claims that WP's HTML5 support wasn't good enough to support YouTube, the problem was WP plays HTML5 video through the built-in system media player and Google didn't want that), and after their collaboratively developed app was released, Google blocked it
again. At the same time, Google wasn't enforcing iOS apps to be built purely with the HTML5 APIs, so literally only Microsoft had to follow these restrictions. The end result was, YouTube was only accessible through the browser and not through an app. Google then followed up these two things almost immediately with an announcement that they were dropping support for syncing Google calendars with Windows Phone.
I'm sorry, but there's no way to be on Google's side during that fight. It was a purely anti-competitive pissing contest. You don't have to be on Microsoft's side, but there is no legitimate way to say that Google wasn't abusing their dominant position over a competitor when it came to how they behaved in the early days of Windows Phone. There was a pattern of outright hostility. Google even said "we know where our users are, and they're not on Windows Phone". Since I was a Windows Phone user, I took the hint and stopped using all Google services. It's petty nonsense, and we all got enough of that in the 90s.