I actually don't blame him here. If Clouse were moving on voluntarily, I suspect he would have been the one to do the signing off and there could have been a fond farewell. This makes it seem like it was Callahan letting him go, and in that case it's probably best to limit the discussion. Most people would likely be tactful, but I suspect it could get out of hand easily enough--and I mean that in terms of sensitivity to Clouse rather than not giving Callahan any crap.