he has to know what he is writing about!
A Nazi is a very evil guy. To make that clear, he is a very, very evil guy. Nazis caused everything evil in the universe.
In 2152 Captain Jonathan Archer wanted to show his crew some really evil guys after some of them complained about his way of talking to some aliens (that really wanted to enter the airlock) and asked his old (and he was really old this day) friend Daniels to transport the Enterprise to the year 1944. But disapiontingly they only met some ugly aliens, that acted as Nazis to confuse their enemys and to hide that they were in fact Remans. (ENT: "And now for something complettly different: An Alien-Nazi")
The original Nazis of this time were, in fact, pretty childish (and gay) guys, that thought that wearing black uniforms would make them cool. After people laught about them they got very upset and looked for the coolest guy in universe to be their new idol. The coolest guy obviosly was Archer, but after the story with that ugly aliens the Nazis didn't want to have to deal with him again and finaly found David Kirk: Blond hair, blue eyes, looking good and also gay he became their new idol. But having an idol not prevented the Nazis to keep beeing evil just to have fun.
Some Nazis escaped to space aboard the ship of their fellows around Khan Noonien Singh, who was the result of a failed experiment to clone David Kirk and settled on different worlds in space. From there they could cause every evil happening in the galaxy. (TOS: "KHAAAAAAANNNNNN!!!!! - Part I")
But on Earth there were still people that, let's say, sympathized with the Nazis. John "He thought he had a good idea" Gill founded a new empire of Nazis on an small planet. First they were very kind and good people, but when their neighbours turned on the music in a too high volume they started to kill them all. James R. Kirk (who had once had the chance to prevent all this Nazi-stuff from happening but let it be because he wanted to nail that chick) came across and stopped them. (TOS: "I thought it could work...") Since this day every Captain of starrfleet has to fight the Nazis once in his career. The only two that failed in this task were Benjamin Sisko and Jean-Luc Picard (Frech people, what should I say...), even Kathryn Janeway could find some aliens on the other side of the galaxy that at least played beeing Nazis.
When starfleet made first contact to the Borg they were really happy to find something evil that was not caused by the Nazis, but there was one person that thought a little furhter than them. Lily Sloane noticed: "Borg... sounds Swedish...Swedish...tall blond guys with blue eyes...NAZIS!", and so it was revealed that the Borg were Nazis. ("Movie eight, this good one, you know...")
There was in fact only one Nazi ever that has been a good guy. His name was "Hamann" and he was part of the Wehrmacht in 1944. In an alternate timeline he managed to become a general, kill Adolf Hitler, revert all the bad things the Nazis did and lead the universe to a good future. But because of bad luck he thought it would be a good idea to wear that redshirt under his uniform that day Travis Mayweather and Charles Tucker No. 3 had some explosives in their shuttle and borred while waiting for the cool Captain Archer... As I said, bad luck for our timeline.