The rabbit is a very harmless animal but the problem is that there is a version of the traditional rabbit that was mutated in a lab and it became highly intelligent. So much that it got to the point that it was going to start causing an uprising of these creatures that actually started to plot against humanity. This was actually a human experiment and we never thought that it would work out so well that they could pose a serious threat to humanity.
The idea they had was to create a rabbit smart enough to learn specific routes in order to send messages into areas that are highly dangerous. Also to deploy bombs and deliver terms of negotiation to the enemies. Things got out of hand and we sent out special alien forces to exterminate all of them. The cleansing took over 10 days but it was completed successfully.