In a vacuum, it's not. The market is completely dominated by Google though, and they exercise that authority and mindshare brazenly, to the point that it's easy to see how it affects Firefox. Firefox functions great. It doesn't function great with Google products/services such as YouTube in this case, which has no real competition. What's someone to do? Switch to Chrome. One might even make the assumption that the repeat offenses over time, across various services, across various fields, demonstrates... malice.