Some people don't even seem to realize what a slug is capable of doing. You've got a big .50 caliber hunk of lead hurling at a target at 1000+FPS .. and it's pretty darn accurate out to a certain distance. If you need to shoot something at 100+ yards, pop a few slugs in that Super 90 or 870 .. and you suddenly have a big honkin' rifle in your hands. Sure, it isn't going to be a precision weapon, but if you are capable with a long gun, you should be able to hit a man sized target for defense at 100 yards or so.
A shotgun is a multi-use tool. It's not just some novelty. If it was, the Saiga-12 would not be in the hands of Russian Special Forces and our cops, military, etc would not have shotgunners, either. You have a vast variety of loads to choose from, and that gives you MANY uses for the scattergun. Anything from hunting small game to defense and everything in between, as well. You just need to set up your shotty the right way for the purpose it's intended for.
The bottom line? Anyone who thinks one should not own a shotgun is a dumb arse. EVERYONE needs to at least have a short defensive scattergun.