That's not charity, though -- that's maintenance, something that's worked out between the secular government and the church. The government decides to support the church, the church is not holding a gun to anybody's head.
And don't tell me they hold the threat of excommunication. That's been shown to be SOOOO effective with CINO politicians!
Germany and Switzerland, for two examples have ecclesiastical poll taxes. The only way out from under them is to apostasize, so yes, you are excommunicated. They do far more than support maintenance of the Church - they pay for its social work as well, and go to support the Vatican. This is why the Vatican has been very close to Germany and the US in the past century - these are her two greatest sources of financial support due to the wealth of the Catholic people and their large numbers.