> it allows for so much plausible deniability and difficulty in identifying who is hurt and who benefits.
The reason you're having trouble identifying who is hurt in this case is because very, very few are, but the people who benefit are generally a large group.
In the worst case of the story in question, if someone donated a large amount to a school and their child was given preferential treatment, the loser is possibly a child whose spot is taken, but the beneficiaries are all the other students of the school, and possibly an additional amount of future (or current) students that would not have been able to attend, if those funds are used to allow more applicants.
> The simplest argument, however, is that the purpose of taxes is to provide the services that a society wants
This is a tax program used to incentivize trade of non-traditional goods, and trade generally benefits all involved. What we have are people that are not benefiting society in a way they could (people saving money that's not being put to use in the economy, but specifically more so than needed to safeguard their safety or way of life), and a program to incentivize them to use it in exchange for goods they desire (recognition, genuine altruism) but might need a push to pursue. That push is the government subsidization of the transaction to some degree.
As subsidies go, encouraging wealthy individuals to give money to causes that have to prove they aren't doing it for profit is probably my favorite. Sure, it can be abused by unscrupulous individuals or organizations on both ends, but I'm confident the social good achieved (over people just hoarding wealth longer) far outweighs the negatives.
> All of the complexity of the tax laws simply enable more and more corruption.
Non-profit deductions are simple. You'll have to do much more to convince me that a few anecdotal misuses outweigh what I see as one of the major causes of redistribution of wealth from the wealthy to the less wealthy over many decades.
The pragmatic approach is to attempt to measure who is hurt and by how much, and who is helped and by how much, before making an ultimate decision on whether this is good or bad. I doubt keying off anecdotal media stories about misuse of a tax law will yield better results than that.