At one point, it was common for layer-type cockerel chicks to be dyed various colors and sold at Easter time. That is now illegal in some places, but still happens in some other places.was wondering what’s all the beef with dyed chickens ?!
There were two problems with that.
Some people considered it bad for the chicks (depending on the dye and the methods, it might be bad or harmless.)
And it specifically made chicks appeal to people that would buy them but probably not take good care of them. The people most likely to buy a dyed chick are the same people least likely to know or learn proper chicken care. So this was bad for the chicks, just because of who was likely to buy them.
(I remember thinking that, as a purely business decision, it was a clever thing for the hatcheries to do: they took the male Leghorn chicks that are least likely to be sold, dyed them, and sold them instead of killing them. But of course being profitable is not the same as being good for the chicks.)
As far as dyeing adult chickens, there are some places that have banned dyeing of any animals. That's based on people deciding it is bad for animals to be dyed, which would include all the various reasons given so far in this thread.