Ian,
I am very busy with dog and cat rescue. I agree with you. People should see the dead animals removed from shelters every day. I don't think anyone "mass drowns" cages of dogs anymore but if they did, that would be a real eye opener and should be a big hit on Youtube. Spaying and neutering needs to be pushed and pushed.
The ones that make me the most troubled today are the pitbull breaders. The most euthenized dog at shelters today are pitbulls. It has nothing to do with their temperment. They are being bred by anyone who thinks they can make a buck. Many end up at the shelter by the time they are a year old.
Susie