That argument does not make any sense since according to the Gospel; it is not the absolute amount of money to donate that matters (parable of the widow’s mite).
I think the “Widow’s Mite” argument is valid - history is filled with examples of people who gave generously while still living in a courtry with well-established taxes and governmental authorities with powers that would make the IRS blush with envy!
,
They still have money after taxes to donate to charity so their opportunity has not been diminished by taxation even though the amount of money they can donate is lessened. Even if a redistributive welfare state is success at eliminating poverty within its geopolitical borders (of course, you would not be arguing this because of the belief that socialism is inefficient at creating wealth), then one can expand their generosity beyond their respective nation-state or ethnic group (the parable of the good Samaritan).
*This is a bit difficult for me to follow - maybe if you were give an example of a country within the past 1,000 that championed socialism and positively demonstrated its success. I am unaware of any.
Additionally, I do not think you will actually find that generosity is a product of any governmental system, much less a method of taxation. Generosity, at least as I understand it, is a personal choice made by individuals who acting from mercy and not from a mere sense of justice. It is true that the works of generous people can truly inspire others to be generous - but, is this the thrust of your argument?
God bless
Tom*
Those catechism entries only prohibit authoritarian system of government such as fascism and socialism; they do not condemn milder forms such as social democracy.