You're right, Hitler was a cult of personality but he was also a Socialist. He was an active member of the German Socialist party before he created his own party called the National Socialist German Workers Party. He never stopped being a Socialist.
Nationalism, of itself is not evil. It can be taken to extremes or it can be as simple of appreciating where you live.
Hitler used nationalism to get Germans to believe in the master race concept. But it wasn't nationalism that killed the infirm, mentally handicapped, gays and then finally the Jews (BTW they didn't start killing Jews until after we were at war with them). Nationalism was a tool used on the people to go along with Hitler but he didn't need their approval. Socialism is what gave Hitler the power to accomplish his evil plans.
It is the foundation of socialism that is corrupt and evil. You have been told all of the wonderful things and all of the great promises that always sucker people into this evil trap. The foundation of socialism is based on a few principles, the worst being no private property rights. The second worst is controlling the means of production. Both of those take all hope from those trapped in its regime.
What you must do is stop looking at those wonderful promises they always make and look at the utter devastation socialism creates. The Scandinavian countries (as much as Bernie wants you to think they are) are NOT socialist. They are closer to socialism than we are but not by much. They are not even the utopias that Bernie says they are. You have to look at the countries that actually practiced Socialism. Germany under Kaiser Wilhelm and Germany under Hitler. The USSR. China. North Korea. Cuba. Venezuela. Look at what it did to Argentina until they pulled themselves out of it. Look at the central American countries who are always fighting to overthrow one socialist dictator with another socialist dictator.
Socialism concentrates all power to the the central planners or the government. It is an oligarchy that is designed to force their citizens to work exclusively for the support of the oligarchs. This is all socialism has ever been.
They promise you a wonderful life without any cares and that the government will take care of all of your needs. That is why so many people are duped into supporting it. It has never fulfilled those promises nor can it. Anyone who understands economics runs as fast as they can from socialism. Socialism is pure evil.