They may have been, or maybe not. I dont think it's really possible to know given so much time and propaganda. However that was not the primary reason for Germany's desire to expand east. Germany's heartland had reached peak population and was lacking in natural resources. They wanted to become a superpower and regarded this as an existential question, so it was essential for them to capture silesia, czechia and other parts of eastern europe. Poland was in the way. Their requirement to invade Poland would have persisted irrespective of what happened in the Danzig corridor. Poland also had core issues at play. They had gone from being a part of a huge empire with plenty of exposure to trade, to being a newly independent state with no access to trade routes except through the territory of their enemies. As such, they *had* to retain Danzig and could not allow a german nationalist movement to return it to German control. If they did they would be permanently weakened and their ability to sustain their independence would wither and die within decades. Convincing the Polish that Hitler was right is a bit like convincing the Irish that Cromwell made some good points. It's just not going to happen.