Let's replace the action of suicide with another action, murder, and see if it changes things:
"Is the verbal urging of murder a cause of his death? Is there a statute forbidding the verbal urging of murder under the penalty of imprisonment?"
Yes, there is. Conspiracy if nothing else. Planning, urging, and manipulating someone into committing a crime is, in and of itself, criminal behavior. When a criminal action leads to a death, those involved can be charged in the death, even if they did not take direct action.
Think about the getaway driver at a bank robbery. If one of the robbers is killed, the driver can be charged with manslaughter or even murder.
Nice analogy but you did not answer my questions. You analogy fails as there are statutes against advocating murder. The statutes involve one person urging a second person to kill a third. That was not this situation.