Sir, it is a huge difference between having the handicap (or the blessing) of a supposed gene of murderer, and actually be a serial killer.
The Bible does not excuse anyone for sin, though sin appears to be so natural. The natural inclination is not a guilt, but the desire, purpose or justification of sin is already sin and guilt, before any visible action.
We are all sinners. While sins are not equal in guilt, they all lead to eternal death, if they are not repented for. In this case, we are dealing with a special sin, that is especially disgusting even for normal sinners, and treated in the Bible as a capital sin. And instead of helping a sinner to repent, people seem to congratulate him/her, justifying the sin and explaining away the Word of God. This is a true sign of the time, more convincing than Revelation 13.