First, let me dispense the semantics issue I have, because it's really quite small. The fifth doesn't specifically mention states, but people. It starts with, "No person shall..." States aren't even mentioned, and aren't even the issue. What is at issue is the liberty of the individual, in this case.
If the argument stands that the federal government cannot pass laws against murder if necessary, then you are in effect saying that the federal government has no power to enforce the provisions of its constitution, and is a dead letter anyway.
The fourteenth amendment mentions the state, to countermand the fallacious argument being made at the time, having far too much acceptance to be ignored, that the Bill of Rights only applied to the Federal Government. At the end of the fourteenth amendment, in case there was still any doubt, it states that, "The Congress shall have power to enforce, by appropriate legislation, the provisions of this article."