'Email marketing' versus outright email spam
While I think that the end effects are the same, I think that there is a conceptual difference between what gets called 'email marketing' and outright email spam, and that this difference influences how the people who originate 'email marketing' think about it.
To put it one way, what I call 'email marketing' at least attempts to be the logical extension of physical mail marketing; you gather the addresses of your customers, of business cards dropped into your giveaway draws at tradeshows, of people who have sent you sales inquiries or requests for literature, 'qualified leads', and so on, and then pelt them with stuff. In the old world you did it with physical mail, and in the new electronic world you do it with email, because it is at least convenient for marketers to consider email the equivalent of paper email rather than a phone call.
(There are some marketing departments that would cold-call valuable customer prospects, but not many of them, and I don't think that they last long. People hate cold calls, and alienating good potential customers is not good business.)
This contrasts with email spammers, who make basically no attempt to restrict who they spam; they'll happily spray random or at best semi-random email addresses, for a collection of reasons.
People who are engaged in genuine email marketing (as opposed to using it as a cover for spam) care both about it going to the right people and it being well received, just as they would care for a paper mail campaign. You can thus at least theoretically influence their actions by pointing out where they fail on both issues. People who are spamming don't really care about either issue, they just care that the response rate is high enough to give them an economic return (and often the answer to that is to spam more addresses).