The most evil men of all time weren't short, or at least most of the ones you listed weren't.

Although compared to today's averages they may seem shorter they weren't of an unusual height for their times at all, when you consider the bad quality and small amounts of food that people received (which inevitably resulted in vitamin deficiencies with inhibit growth) in comparison with today it's not really surprising.

For example Hitler stood at an estimated 175cm (not that this is really considered strangely short today), but judging by the heights of the other Nazis who he was seen around his height was perfectly normal, Himmler was estimated to be just 1cm shorter and Goering 3cm taller.

Napoleon was around between 5'5 and 5'7, so at very worst only an inch or so under average height at the time, furthermore he was usually seen around Imperial Guards who were tall (there was even a height requirement to become one!). Finally, his enemies propagated the rumour of him being short to undermine him, as a result of the nickname 'The Little Corporal' which was affectionate rather than literal.

So, in conclusion, evil men aren't short, they're all perfectly average for their time.