Hey David.
Thank you for that incredibly patronizing, and detailed, reply.
Allow me to reply in kind...
For the record, I am in fact an experienced software developer, that have worked extensively with, and understands well, the inner workings of the internet itself, internet security and email, at a low level.
Fist: about "broadcast email"
This concept is just plain incorrect; the analogy is flawed at the core.
Even when "broadcast" to a mailing list - like in this case - the emails are still sent directly to specific recipients. They are not simply "put out there" and left for anybody who cares to listen. The email protocols, and the very concepts involved, simply do not support that.
Even for people unfamiliar with the technical aspects of email, this is clear from the image I posted earlier.
How often do you turn on the radio, and the radio host greets you (and everybody else listening...) by name? Never, because that is not possible for "broadcast media". Tailored messages like that are only possible in a one-to-one or bi-directional schemas, and even when the messages are identical, on a low level all emails are tailored for specific recipients.
Second: about the security
Pointing out why data encryption is necessary on the internet is pointless; everybody an their grandparents understand that. So I'm just going to assume you realize how sending unencrypted emails exposes their contents to the world.
Even in the absence of "Personally Identifiable Information", like socials or finance details, there is plenty to be learned from a mailing list message. For one, there is always the email address of the recipient. (I get enough spam as it is, thank you.) Also, in this case, the contents of the mail also contain the user's name. On top of that, anybody intercepting this message will easily deduce that I am a customer of Malwarebytes.
You may be thinking that's not exactly dangerous info. You'd be wrong.
I'm not going to go into details about how this could be used for wrongdoing, but I think the Malwarebytes engineers would agree that simply handing this info over to the world is hardly something to be taken lightly.