I don't agree on expecting explanations. There is a good reason not to expect or demand that downvoters explain everything. Downvoting is not rewarded the way upvoting is. Anyone downvoting is either malicious or doing a public service. Malicious downvoters won't explain and demanding more uncompensated effort and explanations from those doing good by downvoting means that less people will be willing to do it.

Just as others have stated that upvotes don't get explanations, downvotes often won't either. Just accept it as the subjective opinion of the voter (even if you don't agree with it) and go on with life (which could include also making your own, contrary vote, or not).