I think this a problem with applications with a privacy focused user basis. It becomes very black and white where any type of information being sent somewhere is bad. I respect that some people have that opinion and more power to them, but being pragmatic about this is important. I personally disabled this flag, and I recognize how this is edging into a risky area, but I also recognize that the Mozilla CTO is somewhat correct and if we have the option between a browser that blocks everything and one that is privacy-preserving (where users can still opt for the former), businesses are more likely to adopt the privacy-preserving standards and that benefits the vast majority of users.
Privacy is a scale. I’m all onboard with Firefox, I block tons of trackers and ads, I’m even somebody who uses NoScript and suffers the ramifications to due to ideology reasons, but I also enable telemetry in Firefox because I trust that usage metrics will benefit the product.