So by restricting what people can use their browser for, you think its more free?
Yes. In the same way as restricting what people can take away from other people's houses makes everyone more free.
You can choose not to use DRM content or you can choose not to
You can't choose not to use DRM once it's required to access most content of the Internet thanks to the fact that Mozilla, too, made it possible.
but if the browser doesn't support it, there is no freedom of choice, is there?
This is an injustice that is to be ascribed by the perpetrators of DRM: Google, Apple, Adobe, Microsoft. Now Mozilla have joined the club of the culprits.
DRM being crackable is not actually that important, what matters is how difficult it is for the average user. You only have to make it slightly tricky or add some slight perceived risk to downloading pirated stuff and they will choose to pay for it instead.
No, skilled users will pirate the contents and serve them to the average users in a form that is even more convenient to consume than the DRM-ridden one.
Refusing to support this part of the standard would have robbed Firefox of more users than they will lose by supporting it.
The EME non-standard cannot be supported by open source platforms. It's not a matter of Mozilla "refusing" to support it, it's mathematically impossible for them to support it in a meaningful way. A EME-enabled site implicitly refuses any user running Firefox on Linux. So it's EME itself that robs Firefox of its users, not Mozilla's decision to support it or not.
The reality is that people who view piracy as some sort of moral duty and right like you do are in the minority, that is why most of the public quite happily go along with more stringent copyright laws being drafted by the politicians they elect.
Even if that were true, it doesn't make those laws any more just. In some places of the world, the vast majority of people believe that gay people should be hanged from a crane in the public square.
I've noticed several design suggestions in your code.