the main issue is that IMO, there are way to much people with "extreme" views on both sides and not enough people "inbetween". while one thinks every dog should be saved, the other side is holding the dogs to a much to high standard (they should NEVER bite a kid for pulling it's ear for ex.) they ARE animals after all.. the good thing to do probably lays somewhere in between. not every dog that bites should be put to sleep, but they shouldn't all be saved neither. too bad there are not enough people to think like that..
However, we did - and still do - have a lot of human-aggressive dogs who I just do not think should be adopted out. One is a bully-lab-thing that misdirects with great ease. She bit me on two occasions, the second one needing stitches. We had another dog who broke a co-worker's arm in two places. (He was sent to a sanctuary, which I still do not agree with.) We have a cage-brave bully-sighthound-thing who, aside from this, bit a volunteer badly. (She is suing the shelter.) We have a dog who has been in the shelter for four years. She came in as a perfectly adoptable 6-month-old pup. She recently attacked another dog and we now have to "hide" her because most people want to be put down.