Phonetically, the pronunciation of the first two syllables, Na and ti, would not be
Nah-Tee, but rather
Nah-Tseh or
Nah-Tsee
You can hear it here (be patient, it might take a LONG time to load):
http://tts.imtranslator.net/Fp5I
or
http://tts.imtranslator.net/Fp4s
Hence: Nazi (phonetically
Nah-Tsee)