Is he a national socialist? I haven't seen any evidence that he belongs to the national socialist party. He is denying the holocaust, not national socialism...
Likewise, the Hitler Youth was a brain washing version of the boy scouts & girl guides, essentially. Membership was essentially mandatory, so pretty much every German who was over 12 by the end of the war had been a member.
It is still an embarrassment for the German people and is one of the things that has shaped their behaviour since the Second World War. The Germans, to a large degree, still shun any form of elitism. Groups like Mensa were shunned here for years, because it was considered elitism and left a bad taste in the mouth of most Germans. This is slowly changing, but it has held Germany back in many areas.