Im not sure why people respond in this way. As you said the fact that he was a member had been known for decades. That he was an opportunist is certainly true, he simply applied for the position of Juliana's consort. In the mid 1930's many if not most descendants of the former reigning dynasties within Germany were party members. It may have been one of the reasons why Wilhelmina had a preference for a non-German son-in-law but her attempts to match her daughter with a suitable Swedish or Greek prince failed.
By the time Bernard showed up they were getting a bit desperate.
I think Annejet van der Zijl's biography on him is really good. Her conclusion that if you invite someone to play the role of Prince Charming you should not be surprised that after decades in that role he starts to believe in fairytales himself.
You are also correct that Bernard probably never believed or adhered to the Nazi philosophy and he did do a lot of good. Unfortunately most of the people he helped are no longer around to keep that part of his memory alive. We should not forget that without him Juliana might very well have been the last Orange-Nassau. The fact that the great court rituals like the reception of ambassadors and Prinsjesdag still exist in their current form is the result of his conviction that monarchy needs a certain level of pomp. Both Beatrix and Margriet have expressed their gratitude about being taken from the school their mother selected to receive a more knowledge based education.
He was one of the founding members of the world wildlife fund and was for years the only person many Dutch veterans could call upon to help them. For years he travelled the globe asked by the Dutch government to bring in as much business opportunities as he could. They gave him money and high Dutch orders to achieve this but never gave him the legal boundaries they expected him to stay within. Unlike Claus Bernhard had no diplomatic and legal training so overstepped what others felt were lines regularly in order to achieve the desired goal.
To me Bernard is a contradiction, the man who helped the House of Orange survive and thrive is also the person responsible for the biggest threats to it's survival.
At this stage it looks like he'll be remembered as the crook. The villain who cheated on his wife and tried to make money for himself. This NSDAP membership card fits in that scenario. That he also did considerable amounts of good is swept under the carpet or simply ignored. In that the haters of him copy the behaviour they accused his fans of by concentrating on one side of the man instead of looking at the whole picture.
I am confused. Why is the existence of the card so significant? Because what it stands for or that he kept it? Why are people (aka the media) acting so shocked he registered himself as a member of the nazi party? Is their memory in such a terrible state? We already knew he became a member of the nazi party and the SA and SS during the mid Ď30. Bernhard was quite dismissive about it because he didnít think too much of it. It served his purposes at the time. Like so many others during that time he joined because it would benefit him. In retrospect many were horrified when the learned what they had backed. People often assume all Germans joined the NSDAP because they fully embraced fascism, antisemitism and the extreme nazi doctrines. Many didnít. Like so many Bernhard was an opportunist. Beside being a narcissist, incredibly shrewd and a convincing liar, he also had some pretty good qualities.
We know he got it through an American army contact shortly after the war. Why he never destroyed it remains a question. The former Queen would never have had it publicised her son stated that he feels history needs to be faced warts and all. He is not happy about his grandfather's membership of the NSDAP before his marriage to the Dutch crown princess but it is part of history. He could easily have followed his great grandmother's example. It has been said that Queen Wilhelmina smoked the fireplaces when she went through the archives of her father, halfbrothers and husband. The current king as a trained historian is more respectful of the evidence. He wants the real truth to come out and has opened the private family archives up until the 6th of september 1948, the day his grandmother Juliana succeeded to the throne.
That means still quite a lot remains hidden. Probably because three of the queens daughters are still alive. Besides the actions of a monarch also have way more weight than those of a royal consort.