"While it was agreed the cats probably help with containing vermin,"
Scientific studies have shown:
“Cats at artificially high densities, sustained by supplemental feeding, reduce abundance of native rodent and bird populations, change the rodent species composition, and may facilitate the expansion of the house mouse into new areas.” (Hawkins, C.C., W.E. Grant,and M.T.Longnecker.1999.Effect of subsidized house cats on California birds and rodents. Transactions of the Western Section of The Wildlife Society 35:29-33)
Taking pity on the unwanted pets enables them to prey on our native fauna! There is nothing compassionate, non-lethal, nor humane about them killing hundreds of millions of our birds, reptiles, mammals, and amphibians each year! Those cats create an environmental emergency, not an animal welfare one!