[StavrosK]

It's wrong for the browser to give me a way to containerize whatever domain I want?

[Ohn0]

At first glance, this seems to be pretty opinionated, with a hip 30 second commercial

https://www.mozilla.org/en-US/firefox/facebookcontainer/

[comboy]

Absolutely not, but you should be the one choosing the domain.

[StavrosK]

I am, Firefox doesn't do this by default.

[gpvos]

Facebook Container is an optional extension, not installed by default. And you can write your own extension for different domains. In fact, people have created several such extensions, such as Google Container, Temporary Containers, and others. It's true though that the Facebook Container extension is actively marketed by Mozilla.