I think it's a pretty fine line. I also think here in the Friends and Family forum we hop right over that line frequently.
Not because we are cruel people but because the conditions and situations found in an alcoholic household can be so ludicrous and by god they are funny sometimes! Someone wanting to run to the liquor store naked is funny. Is it also sad, of course it is. Dark humour.
Living with the madness that is alcoholism is not easy and sometimes we need a laugh and sometimes others will find that inappropriate (we are coming from different perspectives), however I do defend those that need to vent a bit and I personally didn't find this inappropriate at all.
Sometimes you laugh rather than the alternative, which is to cry.