It is said by those who balk at socialist policies of redistribution, the polite ones that is, that you cannot enforce altruism on people.
It seems however that we live more in a paradigm of enforced selfishness.
Witness the increasing out-lawing of giving to beggars, the business and competitively-minded jobs system where you have to put yourself first at the expense of others, artificial scarcity of money and resources preventing people from sharing since lacking and forcing them into competition against one another, monetary pressures to constantly self-promote, a consumption-based economy where everyone is coaxed into being their own materialistic sovereign and so on.
Conservatives will say you can always give to charity and that is more moral than enforced redistribution since voluntary. Yet they do not stop and consider the immorality of the system they promote and support which glorifies selfish greed and pushes ethical people who aren't into money-making into the margins.
In other words, charity, thinking about and giving to others, is the exception that is said to temper the rule of selfish monetary gain. That is to say, selfishness is built in and enforced by the system, whereas altruism is open to people's caprice.
I am not saying I agree with coercive socialist ideals of altruism achieved through taxation purely for the fact that they are coercive but I do not agree with coercive conservative ideals of selfishness either.
Libertarians and right-wingers generally take issue with redistribution through welfare policies and socialised institutions like healthcare with the idea that we do not have the right to other people's labour which is a right they claim socialist taxation pretends we do have.
Yet they fail to see that the capitalism they support entrenches the right to other people's labour through the need to have money to continue to exist in a monetary system and therefore having to sell one's labour in return for often minimal wages increasingly decided at the discretion of capitalist employers.