We have a group like this, which feeds a couple dozen feral cats on "Kitty Cat Lane." Of course there is science behind the insanity -- toxoplasmosis infections from the cats they love.
'Neuter and Release' programs are common, supported and sanctioned by animal shelters, usually local vets provide their services for free, and the point is to provide basic medical for the animals while at the same time trying to control excess populations.
Calling them 'Nutty cat lady vigilantes' would be like calling people 100 years ago providing shelter for abused women 'Marriage Wreckers'.
Enough with the petty, denigrating attacks people helping mostly harmless animals, which is a generally good thing. These rescuers/helpers run 'neuter and release' programs and are keen on having population control, not increasing the number of rogue cats.
Mostly harmless to you... What a strange thing to call what is effectively an apex suburban predator that is known to kill for fun with no intention of eating.
What's nonsense about it? These aren't raccoons digging through people's trash and scavenging, they hunt wildlife for food and are protected from everything that would hunt them in return, even getting food and water and potentially shelter in the worst months.
I think as society sprawls out and folks have fewer kids, this stuff gets escalated.