I live in Maine and only once did I actually put heat in my coop. It was dipping below freezing (I think we were having a polar vortex) and I had a hen who wasn't taking the cold well, so I put on a heat lamp for the night. Other than that, I've never put heat in my coop and speak strongly against it. Heat lamps are an extreme fire hazard, especially when people aren't using them properly, and if there's a power outage, you've lost all your birds. Also, the constant light is bad for the birds health in the long run. They need their breaks on laying, whether we want them to or not, and by them having the 24/7 lighting, it'll shorten their life, especially if they're already prone to laying related health issues.
On a side note, chickens can freeze to death. I've seen it on here and almost lost a rooster myself. It's more of the care of the birds, not the heat, and the breeds. If you have your birds outside or in a drafty coop, then they're going to get cold. Also, coops that are too big to maintain a proper body heat temperature can be bad too (for birds who have a harder time with the cold). Then, if you've got a bunch of Mediterranean breeds, they're not going to do well either.
Maybe it's best to just walk away when someone is attempting to argue with you about your birds. You know your birds and that they are getting the proper care that their bodies are built for. But, you also know the facts of how and why your birds can handle the cold, so it might be helpful to share the facts as well. (Coop setup, breeds, how they actually molt and grow in winter feathers, and if you do deep litter compost, mention that too, etc. Really, if you brought a chicken inside on a cold day to "warm them up," they're not going to be very happy with you and are going to get too hot.)