This line in the article is completely incorrect.
If the money is not donated it is not kept by the taxpayer.
It is kept by the government. No one is saving any money by not approving the donation.
"I quit the church already in 2007," Manfred Gonschor, a Munich-based IT-consultant, said. "It was when I got a bonus payment and realized that I could have paid myself a nice holiday alone on the amount of church tax that I was paying on it."
This guy who has already received the cash says you are wrong...