https://en.wikipedia.org/wiki/Protest#By_Internet_and_social_networking

The link you posted makes no reference to abuse or the success rates of that sort of campaign. (If you want to start a large-scale protest movement, be my guest! That might get the decision reversed. Or perhaps not. I'm not the person who made the decision. But I will say that tens or hundreds of people emailing abusive messages will get ignored at best.)

Could you please link me to statistics […]

Nope. 1) It's not my place to. 2) You wouldn't believe me even if I did. (Nor would you have any reason to. 87% of all statistics are made up on the spot.)

If you perceive emails from users to developers and organization leaders as a form of abuse

Whether email is abusive or not depends largely on the content. The sample email you posted wasn't a good example of the kind of thing that is easy for people to read and agree with, and I believe it would be harmful to your cause. (Yes, yes, I know you said you'd use different language, but you managed to not use different language in your rant, which is what sets the tone of the conversation.) Similarly, I'm sure some people would claim that flooding several irc channels with "And now fuck off you STxPID FxCKING CxNTS!" (that's a verbatim quote, by the way, not something I made up) is a totally reasonable way of influencing the project, and not abusive at all.

Furthermore, if anyone is working at Mozilla, and doesn't understand that there's a (clear and documented) managerial hierarchy, with some people above others, then they're going to be sorely disappointed by reality, no matter what I say. ;)

To conclude, I gave you my honest suggestion for the most effective way I think you can promote your cause. Feel free to follow it or not, and I wish you the best of luck either way.