There are 2 categories these people fall under:
People who don't know, but would care if they did.
People who DO know, but still don't care.
If any of them are in the 1st category, you can ask them if they wish to be responsible for this:
Two uncontrolled breeding cats create two litters per year at a survival rate of 2.8 kittens per litter. With continued breeding, they create:
Year 1 = 12 cats
Year 2 = 66 cats
Year 3 = 2,201 cats
Year 4 = 3,822 cats
Year 5 = 12,680 cats
Year 10 = 80,399,780 cats