50% + 1 is called democracy. Civil liberties are more liable to be swept away by minorities that come to power. In the US, the republicans often do this because they have minority popular support but a disproportionate representation in government. So the key is to make sure that it's 50% + 1 but also representative of the real population.

The nobility is another example of a minority with disproportionate power. It's important that they are reduced to ensure civil liberties.

All other democracies have safeguards against the tyranny of the majority. Whether it is representativity by state in the US or in the EU, a constitution requiring a large consensus to change in the US, or the senate being elected by the elected officials of small cities in France, it is not true that democracy is just 50% + 1 vote.