Counterpoint, no rights are absolute. There are conditions and restrictions on every “fundamental constitutional right.” Freedom of speech does not include slander or inciting violence. Freedom of religion does not protect abuse or acts of violence. Freedom to bear arms does not include weapons of war or negligent behavior.
Addiction is a medical condition, and should not be treated by criminal courts. On the other hand, addiction does undermine an individual’s rational thinking. Should addicts be permitted to carry firearms? I don’t think that is an unreasonable restriction.
The problem with my argument is that I don’t think our restrictions on gun ownership go nearly far enough. Addiction is a problem, but it’s not the most pressing problem we have related to gun violence.