I mean, if we are going to use that button to feel "satisfied" by punishing others whose business practices we or actions we disagree with, rather than to actually mark, you know, actual spam that we shouldn't have received in the first place, why not include some old fashioned tit-for-tat, right?
Seriously: you are abusing the right to be part of a collective spam filter by interpreting the rules of that law in that way. You aren't even doing it in a way that other users of that spam filter are going to obviously appreciate: a lot of people (heaven forbid) actually like receiving the email we sign up for.
Actually, spammy behaviour by "legitimate" senders should be punished, and they will get the message. Unsubscribe should be one-click - email users have enough on their plates already, and if I have done something, however small, to improve the behaviour of mailers, I feel great about that.
That also gets dinged against the sender and an account can be suspended if its too high.
TLDR; you're not using it as it was intended.
MailChimp etc are for messages you explicitly sign up for.
