Irresponsible cat owners are basically ignorant people, often incapable of rational reasoning, so educating them may well be a waste of time. Regional Councils should set up strict rules (no more than 2 cats per household, all desexed, cat run facility, etc.) and enforce these laws. That, in my opinion is the weakest link - e.g. we have laws about barking dogs but the Councils don't enforce them, so the dogs bark their little hearts out day and night. Don't start me on that.
We only have one cat now (desexed male), He stays indoors after dark (no choice given lol) and hangs around the house during the day. He doesn't wonder to the neighbors because they all have dogs. Occasionally, other cats come into our property with the intent to challenge our cat but I find the garden hose very useful to show them the exit. It's not that hard. When Louie (the cat) was young and killed a frog, I minced up the dead frog and mixed it into his food. He walked around the dish, sniffed it, licked it for 2 days but didn't eat it. He never touched frogs again. We have plenty of wildlife in our garden as well as one happy cat and two happy, responsible cat owners.
Colin is absolutely right when comparing the "good snake is a dead one" with the "kill the cat" mentality. Spot on!