In dealing with questions which requires one to make a choice it always becomes a dilemma. This is the nature of samsara. No matter how good our intentions are or how much we try to balance the pros and cons , there is no perfect solution or a win win situation.
It is said that the day we are born into this world , we already cause harm ! Because we are are born from impure causes, we will have to live in an imperfect world whereby no matter how nice and kind we are, we will have enemies; no matter how careful we are, even living in a cave away from it all, we will have to endure problems; and no matter how conscientious we are we will have to make decisions which will create issues for others. It is always the case of the lesser of the two evils in samsara.
Actually if we check the opinions and views of all the contributors to this forum , we will come to the conclusion that the arguments for and against any subject will go on forever without satisfying any party although its good tonic for our mind ! This is due to the inter dependence of all things . When it comes to happiness or suffering, there is no difference between monk and rabbit .
Buddhism's 'middle way ' philosophy, can be a big help in guiding us out of this dilemma by accepting that life is a compromise as long as we hold worldly views and habits. If we do not like to be compromised , if we want to live in a perfect world , the only way is to renounce this world of desire through exercising the Buddhist option by training our mind in achieving renunciation or better still bodhicitta.
If the monk had developed such a mind, whether he kills the rabbit or not for whatever reasons , there will be no karmic repercussions. This is the essential point. For us ordinary people, or even monks who have no such attainments, its suffering whatever we do or not do.