It is stupid because although Hitler clearly wanted to prevent an uprising of the Communists in Germany at the time, it is ridiculous to assume that everyone who wants to take your assault weapons has the same motives.
You can argue that Coca Cola is refreshing, but you cannot assume that Coca Cola is the ONLY thing that is refreshing. Cold water is usually rather a lot more refreshing. I can drink cokes and sodas until I slosh and still feel thirsty.
The logic for posting the stupid graphic is lame and flawed. That is what makes it stupid.
Japan and Australia ban guns, and are not dictatorships. They have far fewer shootings than we do.
Hitler had some pretty good ideas: the Autobahns, the Volkswagen, continuing with Bismarck's Old Age assistance plan.
The whole idea of posting a picture of Hitler is what is called Guilt by Association. It is a type of logical fallacy.
Not everything Hitler did was a bad idea. Not every motivation Hitler had was shared by others who took the same action.
It seems that Eisenhower shared the motivation Hitler had with regard to the Autobahns: Of course, the original idea of a 4 lane limited access highway was the PA Turnpike. But both Hitler and Ike saw the value of fast roads as being essential for moving military hardware. The Interstate Highway System was built for the purpose of national defense, that is what the enabling legislation said. Does that mean the Ike was just another Hitler?
In summary, the use of this graphic is lame and stupid and only appeals to those who are also both lame and stupid.