Animals getting put down for "Aggressive Behavior"

I think there are a few considerations to lay out before we begin. Feel free to let me know if you find any of my assumptions/definitions to run counter to your intention so that I can properly accommodate the viewpoint. How are we defining "aggressive" in the context of the animal's behavior? What is the aggressive behavior that has been demonstrated, in what context did it occur, and what is the risk of it recurring? Are we talking about domesticated or wild animals? To whom has this aggression been directed? Based on the animal's daily routine, who (else) could potentially suffer from the behavior? Defining "aggressive" - I will define aggressive behavior as that which has caused a person (or, potentially, another animal) to be injured or put at risk of injury.Recurrence - To deal with perhaps the most common example in this realm, I will assume we are talking about a dog deliberately biting a person, whether it be out of defense or malice.Domesticated vs. Wild - There may be different viewpoints and contentions should we be discussing a house cat versus a lion. In the latter case, that lion may be held in captivity (e.g. a zoo) or living in its natural habitat. For this debate, I will speak of the most controversial issue - that regarding domesticated dogs and cats.Direction of aggression - Was this behavior directed at the animal's owner? If so, perhaps humans have a right to decide whether to risk injury in order to enjoy the company or protection afforded by a pet. On the contrary, perhaps an action directed at an owner could later be directed at a non-owner, in which case the incident was merely anecdotal. Let us assume, for the sake of this argument, that the aggressive behavior was directed toward a non-owner.Routine - Does this pet spend 99% of its waking hours in the confines of its owner's home? Or, is it regularly walked and brought to parks where it would be free to interact with non-owners? Let's assume the latter.--Aggression is primarily triggered, particularly in animals, by a 'fight or flight' response. This response is a purely physiological, neurochemical, and thus unconscious reaction to the perception of threat. To 'fight' is to combat the threat with physical aggression,while 'flight' is to combat the threat via physical removal of fleeing. More specifically, this response is a neurochemical process that beings in the amygdala which triggers the activation of the pituitary gland which, in turn, leads to a rapid release of catecholamines (e.g. cortisone and hormones (metabolites of cortisol), adrenaline, and nonadrenaline. The release of these chemicals causes actual, bona fide structural changes to the animal's neurophysiology. These changes are particularly designed to grant the animal with sufficient energy to resolve their situation and avert the threat (or perceived threat).There are a number of factors that precipitate the decision between 'fight' and 'flight'. For example, genetic predisposition may cause an animal to be more likely to exhibit aggression. An animal who has just given birth and is caring for its young will also be more likely to respond with physical behavior.Animals are unable to experience or comprehend complex emotions such as shame or guilt and, therefore, cannot understand the degree to which owners and/or non-owners find their behavior to be reprehensible. It is possible that animals can be conditioned to avoid some behaviors through infliction of pain or withholding of nutrients, but this is not tantamount to a conscious understanding of the implications of their aggression. Furthermore, in cases where dogs have bitten and severely injured humans, few remedies ranging from medication to kenneling to relocation have been shown effective.If aggression in dogs and cats is primarily triggered by an unconscious chain of events AND the animal is unable to understand the negative externalities caused by this chain, it is between fairly and highly unlikely that they can effect instinctual change. This is all to say, once such a pet exhibits severe aggression, it is extremely likely to recur, especially should similar circumstances and environments arise.There are a number of reasons why such an animal should be euthanized. Non-owners are, by definition, non-consenting agents who did not voluntarily submit themselves to be in the presence of aggressive animals. Thus, it would seem highly unfair to put such an agent at risk of physical and/or emotional harm when they were not given the opportunity to weigh the costs and benefits that come along with being in its company. Additionally, there is a legal risk carried by the owner in the event that another act of aggression occurs. There is, further, the emotional and financial penalties incurred should another person be placed in the hospital, disfigured, or worse. Even in the case where the owner is the victim of the aggression, they may not have the freedom and latitude to spend 10 months recovering from a debilitating bite to their leg that requires 400 stitches or surgery. There are even more hazards including loss of homeowners insurance and fear of future attacks/aggression.Then there are factors that must be considered on behalf of the pet. If the pet's primary form of "leisure" or "exercise" is enjoying a day in the dog park, but they must avoid doing so for risk of aggression toward non-owners, is that a fair compromise to their quality of life? If the proposed course of action is in some way physically reprimanding the animal when behavior tends toward aggression, is it fair to cause them to live in "fear" pertaining to retribution for their unconscious (re)actions?I have nothing but terrible sympathy for pet owners placed in a position where their dogs or cats must/should/could be euthanized. That said, given the potential compromise on quality of life for the owners, non-owners, and even pets themselves, it seems only humane and responsible to put down animals for "aggressive behavior".