The same topic was the subject of a conversation about ethics that is relayed on the Canadian Museum association website here: http://www.museums.ca/?n=15-293-295
Sergio Munoz Sarmiento has a whole blog dedicated to deaccessioning: http://clancco-theartdeaccessioningblog.blogspot.ca/
I would make sure to draft a detailed deaccession policy in accordance with your collection mandate/management policy. I found the chapter on deaccessioning of the “Museum Registration Methods” very helpful to write our deaccession policy. Try to work out every possible scenario and how the deaccession could impact positively and negatively your collection and museum.