"Email spam, also known as junk email, is unsolicited messages sent in bulk by email"
If you've never spoken to this person before, you have no business relationship with them, and they have not opted in to receive mail from you, you are an email spammer. You can mince words if you have to to sleep easy at night, but this behavior is wrong.
The author of the article did something shady and you are defending him.
Then only options I see is to a) hope google finds you interesting enough, b) paid advertising, or c) word of mouth.
What are the other methods ? I am asking because I can't think of anything else.
1) If the mail you receive actually interests you, you wouldn't classify it as "spamming" ("Did I really sign up for that? Anyway it sounds good"). If not you may avoid them in the future, but you would not have bought their product anyhow.
2) Scale: If a (real) spammer sends out 20 million emails and 0,0001% buy viagra. Thats fine for him. The other Emails cost him close to zero, so every sale it profit.
Of the two above, the latter is probably the spammiest, and might technically count as "spam" since they're unsolicited, but they're generally (in my opinion) targeted sufficiently well enough to be acceptable/tolerable. In excess, though, they can quickly cross that line into being unquestionably spam.