Properly handling opt-outs is part of it. MailChimp does the right thing by soliciting feedback, including the option "I never signed up for these emails", hopefully that goes into whatever scoring mechanism they use to kick out abusive customers. Sadly the current state of what passes for front-end development is abysmal, with pages often not working if a user has cookies or javascript disabled, or an ad-blocker.

As for JGC, he deserves credit for doing the right thing, but that does not change the fact his company violated the law, and their marketing department richly deserves any fire and brimstone is raining down their necks right now. I would say most companies should probably have their email service provider contracts controlled by legal rather than marketing, most marketing departments have an inherent conflict of interest in this regard.