To remove all and then hand pick the ones you like, it seems that you can "select all" and then move them over, then add the ones you like.
I guess a better way to do this would be to default everything to "not accepted" and then ask the user: "what do you want to import?" with the option: "Everything!"
(FuseCal Developer) We're working on a revamped event selection UI right now which should be out in a couple weeks. It will make the simple cases of selecting all the events or just a few of them much easier.
On the example calendar, I think it would have been better to have the green box on the left and the red box on the right. Drag and dropping things from left to right rather than from right to left is more instinctive from a users point of view because one would normally read from left to right (most of your target audience would anyway).
I guess a better way to do this would be to default everything to "not accepted" and then ask the user: "what do you want to import?" with the option: "Everything!"