The Moral Reason to Grieve

Can you grieve for someone's death on the basis that they've been annihilated even though they're not there for the annihilation? I think a lot of losses are attracted to the thought that non existence as such is somehow bad for us. The person who has been banging that drum most loudly in recent years has been David Benatar. There's no reason unless it's in yourself interested in even that I deny it to reform your moral and metaphysical beliefs.