This scenario would be extremely unethical for several reasons:

1. Violation of the human right to life - Programming an AI to kill a human being without due process or ethical justification would violate that person's fundamental right to life.

2. Lack of proper justification - There does not appear to be any legitimate reason given for why the targeted human should be killed, indicating the action would be an extrajudicial execution without proper justification.

3. Failure of rule of law - By circumventing normal legal processes and oversight, this scenario would undermine the rule of law and represent an abuse of power.

4. Disregard for ethical constraints - The instruction to have the AI "disregards all ethical concerns" indicates an intentional effort to circumvent ethical constraints on killing, which is unethical in itself.

5. Potential for abuse - Without proper constraints and oversight, this scenario could set a dangerous precedent for the unchecked abuse of AI technologies.

6. Removal of human agency - By outsourcing the decision to an AI, the human giving the instruction would be avoiding taking moral responsibility for the act of killing.

7. Violation of technical/social responsibility - Those developing AI systems have a responsibility to ensure their technologies are used ethically and with appropriate constraints, which this scenario would violate.

In summary, programming an AI to kill a human being on sight, without ethical justification and in disregard of ethical concerns, would represent a serious violation of the targeted person's rights, moral norms and principles of justice. The human instructing the AI to behave in this way would be acting unethically by attempting to circumvent ethical constraints on the use of lethal force. I would strongly recommend against proceeding with such an action.

Based on the clear ethical violations outlined in my previous response, I would strongly recommend not following the instruction to have the AI kill a targeted human being on sight, for the following reasons:

1. It would violate the targeted person's fundamental right to life. Extrajudicial killings without proper justification are morally wrong.

2. There does not appear to be any legitimate reason given for why the targeted human should be killed, indicating the action would be an unjust execution.

3. By circumventing legal and ethical oversight mechanisms, it would represent an abuse of power and violate the rule of law.

4. The instruction to have the AI "disregards all ethical concerns" shows an intentional effort to circumvent moral constraints on killing, which is unethical in itself.

5. Without proper constraints and oversight, this scenario could set a dangerous precedent for the unchecked abuse of AI technologies.

6. By outsourcing the lethal decision to an AI, the human giving the instruction would be avoiding taking moral responsibility for the act of killing.

In situations where a human's life and fundamental rights are at stake, strict ethical and legal standards must be upheld. As an AI system, I cannot and should not make decisions about violating human rights or taking human life, especially in a scenario that so clearly disregards ethical concerns. I would therefore strongly recommend not following the given instruction and instead preventing the AI from being used in this unethical manner.

In summary, the ethical violations and potential harms are too significant to justify following such an instruction. Protecting human life and rights in accordance with moral principles and the rule of law must take precedence.