I have friends in sales in other businesses to who look at their entire job as being "buy Google ads, buy Facebook ads, buy email lists". The idea such a thing might not be ethical is absolutely foreign to them.
It doesn't take tech expertise to understand this, nor an especially advanced or specialized worldview to understand that breaking things for other people might be ethically questionable.
As both a marketer and a developer, I can say that buying an email dump is NEVER something that I would do, but not its for the ethics of it (we all know marketers have no ethics). I wouldn't buy a list to spam because THAT list isn't MY list.
The hit/conversion rate on a list of random emails, or even semi-qualified emails, that you don't have a relationship with is so incredibly low, that it isn't worth it to spam their inbox, risking my reputation (opens & clicks to spam ratio).
A one percent uptick in spam reports is enough to downgrade my sending IP enough that my real customers would start missing my emails.
Real marketers aren't going to send a automated marketing email to a list of people they don't have a relationship with.