I also agree with @Sailsman63, you are not too protective.
That gives an even better point imho, which is that you clearly aren’t interested in what they have to say. Ergo any email to you is spam. And the way (topic-based-conversation) and options you do have as a user of discourse take great care about that imho.
However, I do see an important usecase for such a feature: security and important system notices. Let’s say the admins of a forum switch to another login-system and want to give their users a heads-up about this or – even worse, but we have to consider it – the system got compromised and passwords have been reset or private data might has been leaked. In this case I’d consider it the Administrator duty to inform even those, who’ve not been active as their data might as well be compromised. Neither of those are critical and wouldn’t be able to be done through an export function I suppose though and I am absolutely against the marketing-approach of things.
On that, though, discourse does know more about the activity of community members than a random mailchimp or many other tools. One feature I particular like about meetup is their selective “email”, where you could say only those should receive the email, who are registered for a certain event or have RSVPed yes in the last x-month. We do use that feature as a last-minute notification of changes (for e.g. a different venue or time), when it is unlikely the receivers have the possibility to look at meetup.com again before the change is due. If it ever comes to an “Event”-Archetype, I assume we do want this kind of feature on that at least …
As you can see I am highly undecided on this but I do see relevant use cases while being against a common easy way of spamming people…