You can remove them from your followers list, as I've just outlined for another Blipper in this other post here.
Stopping them from seeing your journal is different, and the only way to guarantee that, would be to change your journal's settings (Settings - Journal entries - tick the "Protect your entries" box, and note what it says that this does).
The downside of doing this, is that then only your followers can then see your journal. Which can mean, say, that any family and friends that aren't on Blipfoto, but look in on your journal - well, they'll no longer be able to do so. They'll just see one of those messages, "This user's entries are protected." So you may exclude many more than just that follower... i.e. everyone that isn't a follower!. It's also likely to impact on your account in other ways - possibly excluding your entries from being seen in challenges, and the "Popular" pages... if your into those kind of things.
Hope that's of some help, and don't forget, do contact Blip Central if anyone on the site is giving you cause for concern.