Slubber, try and see it for another viewpoint, please.
Compared to those who don't do any of those things, of course the type of dog owner is more responsible, but that is not the point.
The point is that responsible potential dog owners have two options, to buy a dog or rehome one. If they make the decision to buy one, that is one dog less for rehoming, therefore one more for being killed, so yes, they are responsible, indirectly, for their death. It doesn't mean they are immoral necessarily, as they don't necessarily know this, but the fault is still there.
As for people wanting a particular breed, especially a pedigree one, what possible justification can there be for this other than vanity? When we are talking about vanity versus the life of a living creature, morally it is clear which should come first.
Lastly, you say that you have lost respect for Valhalla as a poster and source of knowledge about dogs. This is just ludicrous. Just because she has a different viewpoint from you about this issue does not mean she is any less knowledgeable. That remark just makes you look silly.