I don't think it would. I don't think people understand that gifts are not taxable unless they are over a certain amount.
The reality is that people would no longer receive a deduction for their charitable contribution. I don't think that would make them stop giving.
But if it did, that would only cause the government to give more. So in the end, the government would be paying 100% of the "charity" instead of giving a tax break on say 20% of the charity.
I think it is an emotional thing. They hate religion so much they can't look at it analytically.
The reality is that "taxing churches" is not the same thing as "not making the giving tax-deductible". You need to start listening to what people say, instead of to what you want to think they're saying.
And don't even get me started on "And it'll be okay, because government will just give more, and that's the same." Government =/= charity.
They can’t tax donations below a certain threshold.
For the 1432nd time, there is far more to it than just $5 put in the offering plate.
The US Internal Revenue Service (IRS) classifies churches as 501(c)(3) nonprofit charitable organizations, which are exempt from federal income tax and are able to accept tax-deductible donations. [
1] Unlike secular charities, however, churches are automatically considered to be 501(c)(3) organizations, and, while they may do so voluntarily, they are not required by law to submit an application for exemption or pay the application fee (up to $850 as of Oct. 24, 2011 [
42]). [
1]
In addition, using a benefit known as the "parsonage exemption" (or "parish exemption"), "licensed, commissioned, or ordained" ministers of religion may deduct most of the money they spend on housing from their federal income tax, and these properties are often exempt from state property taxes. [
41] [
43] [
44] The exemption has existed since 1921, and no equivalent tax break is available to leaders of secular nonprofit charities.
Background of the Issue - Churches and Taxes - ProCon.org
I don't personally know of any church which records its offering donations individually. Every church I've ever gone to counts the contents of the offering plate (separate from money specifically designated for tithes, building funds, etc.) and then enters them in the books as a lump sum for that date. Depending on the size of the congregation and how generous they are, that's pretty much going to blow past your "clever" gift scheme.
Also, why should churches - out of every charity and non-profit in this country - be limited in the donations they're allowed to receive, or have their donors limited in how much they want to contribute well beyond the limits already imposed by what can be deducted from one's taxes, so long as they're actually using the money to fulfill their stated purposes, rather than amassing personal wealth for the leaders?