Hitler was an anomaly. Khan was the result of deliberate tampering of the human genome. If Hitler had been the result of any specific human intervention, it's a safe bet that action would be prohibited now.The speech was a load of cobblers. Imagine this sentence in Trek on 22nd century ENT, 'for every good German, there's an Adolf waiting in the wings, so it's my duty to keep Germans from joining the UE army or Starfleet.'
Absolute tosh!