In spite of that, he was friendly, and I recalled that Mr. Frank had been aware of this man's membership in the Dutch Nazi Party before he'd gone into hiding, since the man had worn a party pin under his lapel. I remember that Mr. Frank had commented, "This man you can trust. I know he's not a Nazi at heart. He must have joined the NSB because he was hanging around with a bunch of young men who joined. Being a bachelor and needing a social life, that's why he joined too." Which theme can be inferred from this excerpt?]