I have been discussing with someone about moral responsibility with regards to determinism, free will and compatibilism. 

Compatibilists often claim, as per David Hume, that the agent has free will because they are not being physically coerced to do something by another agent. However, a hard determinist such as myself will simply claim that that coercion is internal, and not external. The causal process is what makes an agent do something, and this may take its form in other agents, genetics, biological influences or the environment. Either way, the variables are out of the control of the agent at the time of making the 'decision'.

This then has implications on the moral responsibility of the agent and thus how we punish them. I claim that retributive punishment, in terms of vengeful tit for tat, is pointless in and of itself because the agent does what they do because they are who they are in the environment they are in, all of which is outside of their control at the time of doing it. Punishment should be used as a consequential deterrent, both for the agent, and for others influenced by this variable.

It comes down to free will being defined by the ability to do otherwise in a given situation. But the causal process makes one do one thing and one thing only. I deny what is known as the Principle of Alternate Possibilities. Thus I deny free will.

The idea of moral responsibility abrogated by genetic or other influences is prevalent in law today. As the New Scientist stated back in 2009:

"A judge's decision to reduce a killer's sentence because he has genetic mutations linked to violence raises a thorny question – can your genes ever absolve you of responsibility for a particular act?
In 2007, Abdelmalek Bayout admitted to stabbing and killing a man and received a sentenced of 9 years and 2 months. Last week, Nature reportedthat Pier Valerio Reinotti, an appeal court judge in Trieste, Italy, cut Bayout's sentence by a year after finding out he has gene variants linked to aggression. Leaving aside the question of whether this link is well enough understood to justify Reinotti's decision, should genes ever be considered a legitimate defence?"