First of all Kirsten I certainly would dispute whether Cats should be outdoors.
Ebony Beau Tubster , Golden Rod , Ebonite , Orange Blossom and the Scratchys would all be alive had they been Indoor Cats , as well as the Many Cats we see who have been hit by Cars.
Indoor Cats are a lot safer and as a Multi Cat Giardian I would day that there can be personality clashes , but that they generally work themselves out .
And My Indoor Cats are happy , I try to leave toys about so thier minds stay active!
And the fcat that some of My Found Cats have had 15 hapy yeras with me disproves this authors point.
You are a very Good Guardian Kirsten , sometimes writers say something cotreversial as a selling point for thier books , whether they believe them or not.