I need to win an argument about fixed gears

Curiously, the Nazis came to power in Germany through the ballot box but were only removed with violence.

Clive, the NSDAP did not come to power 'through the ballot box'. What you must be referring to is the fact that up to a point, the NSDAP's experience of its failed coup in 1923, led it to overtly proclaim conformity to the constitution and the law ('the means, though not the ultimate goal'--which was to eventually overcome it), although they of course also used multiple illegal and covert means, such as terror against their political opponents and in the streets. In particular, the majority for the decisive law that enabled the government to govern without parliament, the Ermächtigungsgesetz of the 23rd March 1933, was created by prohibiting the KPD and murdering, excluding or intimidating other members of parliament.

The biggest percentage of the vote that the NSDAP ever achieved 'through the ballot box' was 37.3% in July 1932, and 33.1% in November 1932 in the last moderately democratic elections in Germany. It is doubly tragic that it is reckoned that their popularity was already falling again when they came to power in a coalition government with centre-right parties (which the latter had implored the president, von Hindenburg, to create).

The next elections in March 1933 were already profoundly undemocratic, with massive voter intimidation (which, by the way, had already been a feature of earlier elections, albeit on a smaller scale) and terror against political opponents (the infamous "Reichstagsbrandverordnung" saw many SPD and KPD members arrested, interned in concentration camps, and physically abused), and still 'only' yielded 43.9% for the NSDAP. The reason why, on paper, the NSDAP then had the absolute majority of seats in parliament was because the seats of the KPD, which had 12.3%, were simply cancelled. With that, the influence of the centre-right parties that had so naïvely assisted Hitler was also bulldozed out of the way. Needless to say, the following one-party elections resulted in the tragic picture that is so familiar from totalitarian régimes the world over.

While it is true that Hitler's entry into government was legal according to the constitution, of course this famously revealed considerable democratic weaknesses in the constitution. The most striking of these was that Hitler was effectively able to suspend democracy through passing the Ermächtigungsgesetz. All other political parties were prohibited by July.

There were multiple other factors playing into the hands of the NSDAP, such as the 'Prussian Coup' of July 1932 in which the stable SPD-led government of Prussia (effectively two-thirds of Germany) was replaced by an unelected governor, the hapless Franz von Papen (greatly facilitating Hitler's later totalitarian transformation of the state), the fact that parliament was hung and successive governments in 1930-1932 were very weak and made many mistakes, and the fact that the upper echelons of the centre-right parties in Germany were anything but democratic (they exerted pressure on von Hindenburg from at least 1932 onwards to make Hitler Chancellor, and although to his credit von Hindenburg refused for a time, he did eventually give in owing to false reassurances that in a coalition government 'framed' by centre-right parties, Hitler would pose no danger). Prior to coming into a coalition government, of course, the street battles between the communists and the SA had already greatly contributed to destabilising the state (and were the pretext for the Prussian Coup).

Please be very careful when trying to simplify complex matters like this. Violence and terror played a very large part in the NSDAP's rise to power. This would never have happened had they used only democratic means.