If you disable the filter, the app doesn't block the user anymore. The unblock button only unblocks until the next time the app sees a bunch of spam from that account. You have to disable the filter to stop that behavior.
Discussion
You guys are missing the point. We can have our cake and eat it too: have spam filters, but if the user unblocks one of the accounts caught in the filter: RESPECT THE USER'S CHOICE! That's the heart of the issue. If the user unblocks someone, don't revert their actions against their consent.