While much taxation is used for the supply of common goods (eg roads, parks etc), governments of most modern social-democracies take a significant proportion of GDP for the purpose of simply giving it away. Ostensibly this 'churn' process is about taking from the rich and giving to the poor. In practise, is frequently about giving to groups favoured by the government (those with 'families', or 'single parents' etc).
It is justified on humanitarian grounds, to increase equality of opportunity, to give a 'leg up' to those at the bottom, to provide a safety net to those who have lost their way, to improve 'social cohesion'.
In fact, it is a form of slavery. It is forcing someone to work for the benefit of another.
While some might argue that no force is involved (because no-one is forced to work), saying in effect 'you don't have to work, but if you do, then 50% of that work must be for the benefit of someone else' is an application of force.
The practise has no more moral validity than slavery.
This is not to say that wealth redistribution is immoral. If an individual chooses to give their wealth to others, they are perfectly entitled to. But they have no right to force others to do so.