I have had the same issue, which is why I created tracker MDL-49029 -- please vote on this.
Normally, role restricting could be done at the activity-level in the permissions. The Choice module, however, does not have a specific "view" permission, therefore, one cannot turn it on/off per role (other than hiding it or grouping it). I haven't tried this yet, but it is possible to make groups on the front page, then as suggested, you could group the choice module.
I agree, despite the fact that guests don't have access to making the choice, I only want authenticated users to see this activity at all.