why shouldn't you make a pet of a rooster
That's a really sitation dependent answer.
Some folks are in the camp that roosters cannot be pets, and should be considered intact male livestock. This is not untrue.
Others consider their cocks pets, and should be treated just like any dog or cat. This is also not untrue.
Personally I find it to be very dependent on three factors: the breed, the individual cockerel, and the owner of the flock.
I find it beneficial to ignore and avoid socializing with roosters of large breeds and hatchery origin (these are the most common cocks to turn mean). I single out this type of bird for two reasons. The first is that these roosters can do the most damage should they become aggressive; a large Production Red or Barred Rock, for example, can do some serious damage should they have half a mind to. The second is because, as a rule, hatcheries are lazy. They pay little attention to the personality of their breeders and allow aggressive cockerels to breed. This yields aggressive offspring. Breeder birds, on the other hand, I would have no problem making pets of, regardless of size. This is because I trust the breeders to have done their jobs and selected for birds which respect their keepers. I see it to be less of a problem to socialize bantams or small egg production breeds, even if they are hatchery sourced. (Though I would still trust a breeder bird far more). Firstly, although a bantam cockerel can still give a good bite or kick should he want to, he cannot cause the potentially serious injuries a standard sized cock could. The smallest ones, like OEGBs or Seramas, are scarcely more than hilarious when they become aggressive. Secondly, bantams have always been considered ornamentals and pets, and as such their personalities have not deteriorated so badly under the lazy breeding of commercial hatcheries, since less pressure has been put on them to produce and they started out with generally very friendly temperaments. However, this brings me to the second factor.
Individual cockerels may become aggressive regardless of their origin. A cock could be from the friendliest line of roosters in the country and still take up a whim and become an ankle flogger. You just never know until they reach maturity. Some consider it inappropriate to ever make a cockerel a pet, simply because he even if he is of a breed or strain known for friendliness, as he may be one of those individuals. It is true that you cannot predict with 100% certainty a cockerels tendency toward aggression, and therein lies the owner's part in all this.
What are you, the owner, willing to do, should a cock become aggressive? Will you cull him or allow someone else to cull him should he become aggressive? Are emotionally capable of spending a long time raising this bird, attempting to make it friendly, only for it to turn around and bite the hand that feeds? It is of my opinion that anyone willing to take the necessary measures to remove aggressive cockerels from their flock should spend all the time they want making pets of roosters; that is certainly how I myself approach the issue. I love my pet roosters, of which I have several. In socializing them, I took the chance that they would become ankle floggers. Certainly, a few did. They were culled. An aggressive rooster does not see a human as a friend or beneficial influence; rather, he sees you as a potential threat or an intruder on his territory, and by socializing him all you are doing is removing his fear of you. Chickens are not brave animals; regardless of their tendency toward aggression, it is very unlikely a cockbird is going to come after a large, predatory animal which is five times his height unless it has given him a reason to think it will not hurt him; e.g., handling him Ina. regular basis and getting him very used to your presence.
