You've called people rude for feeling strongly about their objections to this change, you've denied that Mozilla would have shipped a negative change, you've accused the detractors of this change of not understanding that it could pose a maintenance burden to keep it optional, and you've asserted that said maintenance burden outweighs the usability benefit of letting existing users keep the existing behavior.
You've done everything except provide an actual argument in favor of why Mozilla should introduce this new UI behavior that breaks existing conventions and interferes with other features in ways that are as-yet unresolved.
And you're doing similar stuff elsewhere in the thread about other questionable Mozilla UI decisions.