Anybody that says cats aren't a threat to chickens is completely ignorant.....
Cats eat birds, chickens are birds. Simple as that.
Granted your fluffy mostly indoor, never hungry pet cat poses LESS of a threat. I deal with it first hand almost on a weekly basis. Where I live people love to drop off unwanted cats, they figure it's the country so is ok.
I have a constant supply of wild cats that are always trying to get the birds. Even pet cats kill just for fun and some will kill chickens, just the way it is.