If you collect emails with an opt-out method you shouldn't complain when some people flag you for spam.

Paying customers didn't unsubscribe because they obviously had a higher level of engagement with the service. Of course free users won't keep track of every service they've signed up for, ESPECIALLY if they didn't explicitly say they wanted to be emailed.

I'm not a fan of freemium either, but this is more of a knee-jerk reaction to a perceived insult than any real insight into the business model.