To get to the point, people like Chris Mathews have stated for years North Korea doesn't have nuclear weapons. Their distinction between a nuclear device, which they recognize they have, and a nuclear weapon is the presence of a delivery system. And thus until North Korea actually fires a missile with a live nuclear warhead against a target, These nay sayers will continue to claim the North Koreans don't have a nuclear weapon.
The significance between this and Hitler's death camps: the people were forcibly delivered to the gas chambers, not the gas chambers launched against the people. For it to be a chemical weapon it had to be employed/delivered. Further there has to be an expectation of a similar response. If North Korea was to fire a live nuke, there would be an expectation of a military response. Hitler never employed chemical weapons during the war simply because of the fact the allies would respond with the same.
Some facts when it comes to the second World War. First, Germany stockpiled Sarin nerve gas before the war began: estimate 45,000 tons by 1943. The German Army also required their troops to always carry a gas mask: this was an item that was never present on American and British troops. But with the exception of a couple of cases in 1942 and early 1943 when rogue Army units employed CWs they had with them, the German Army didn't employ chemical weapons. It is reported that after being asked by Goebbels and Bormann to allow the use of Chemical weapons to stop the advancing Russian Army, Hitler, upset by the previous uses without his authorization, ordered that any further use had to be approved by him. And as the Americans and British drove up through Italy, not only did Hitler order that any stocks of German Chemical weapons in Italy, or Italian CWs, be destroyed. Hitler made sure their would be no use by rogue units or officers following the previously mentioned actions in 1942 and early 1943.
And Hitler's concern, that the allies would respond with even more gas. He had been informed that German intelligence expected that the allies had twice as much poison gas as the Germans. In point of fact, because of a rumor that Germany would actually implement gas warfare to defend Italy, a shipment of 2,000 mustard gas bombs were sent to Italy by the Allies. We know of these bombs because the ship they were on was hit by a bomb during the German air attack on the Harbor at Bari Italy. Over 600 sailors and medical personnel were victims of these bombs, which the allies wouldn't admit were there since they were only sent to be used if the Germans used Chemical Weapons first.
Now that these facts are on the record, what did Hitler do in his camps. The death camps used cyanide gas, no different then that use in gas chambers at American or European prisons until the 1980s. Hitler took the cold bureaucratic system for dealing with criminals to the nth degree as he killed whole races and religious groups. And when they were not using cyanide, they had vans rigged up to kill people in them by ducting the engine exhaust into the passenger area. In this case the poison gas was Carbon Monoxide, no different then when people start their car in a closed garage and then just wait for death. The gas is poisonous, but its not a chemical weapon.
Now for the true point in all this. People are falling over each other to try and claim Trump didn't need to fire missiles at Syria. Some are claiming what happened in this town in Syria is a false flag operation since its the only such incident- running in line with the claims of Vladimir Putin. Others want to claim its no different then the use of a bayonet or a gun. The real issue is the number of these incidents that have happened since the Civil War began: incidents that are not always in the Newspapers or News at 10:00. At present there are over 60 reported cases of the use of poison gas by both sides in the war. Cases involving the ISIS group tend to involve Mustard gas. Cases involving Sarin tend to point back to the Syrian Army as the source. But Sarin is not the weapon of choice for Assad; the weapon of choice is Chlorine gas. Its lethality has been known since World War 1, but since its use to purify water it is not identified as a banned weapon by the UN. Thus numerous CW attacks by the Syrian Army that have injured hundreds of people get little or no attention because the chemical has "practical" uses.