That page should also contain a dialog box to make sure the user understands what opting out means. The User should also receive a confirmation e-mail reminding them where to sign up again if they choose to do so. This confirmation should also remind the user of the value the opt-in program has. It should also contain an easy path to sign up again, if the user changes their mind. Reward them for coming back in .
Customers change their mind all the time.
Get used to it. Your opt-in community has a certain degree of novelty. Sometimes that's reason enough for a user to sign up. As that novelty wears out, so does the interest in it. If you are not continually adding value to the community, your mail will be seen as clutter.