I'm not going to worry about the "extinction of domestic dogs" while we're still euthanizing millions of unwanted dogs every year -- many of them young and healthy, and quite a lot of them "purebred".
As for the "extinction of purebred dogs", I seriously doubt that will ever happen, but it's a prospect that I find far less worrisome than the continuing abuse and suffering of so many dogs -- both purebred and not. The world can live without purebred dogs, just as well as it can live without purebred people.
Yes, but people are more likely to care for something if it costs a lot. Which is why pet adoption agencies insist on a fee, even if the money isn't enough to compensate for the cost of running the shelter.
"As for the "extinction of purebred dogs","I find far less worrisome than the continuing abuse and suffering of so many dogs --.. The world can live without purebred dogs, just as well as it can live without purebred people."
You don't mind if purebred dogs die because other dogs are dying. Death as a solution is pretty standard fare for animal rights types as well as calling for death for some peoples.