People that don't own cats and dog don't cause this problem.
The problem is not the presence of the animals in the shelter.
The problem is the lack of regard these people had for proper termination procedures.
Those who view animals as creations of God tend to dispatch them as humanely as possible, believing that they will be held accountable before God otherwise.
Those who view animals as being below us in the evolutionary chain have fewer compunctions engaging in animal cruelty.