If the recipient wants to unsubscribe after receiving an automated email, then by definition that mail was spam to them (literally unwanted mail). So marking that mail as "spam" is the correct thing to do, and nobody should care about the sender's feelings nor should they abide by the sender's pleas.

It is up to the sender (1) not to gaud people into subscribing to their newsletters in the first place, and (2) to send actually useful and interesting content to their subscribers.