The problem has been that the courts sided with the federal government, and it has only been in recent years that churches have had the wherewithal to challenge the law. However, victories against it have only kept churches from losing their status and not overturning the law. The root of that problem is that until the 1930s-1980s churches tended to stay away from politics and encouraged their members to do the same. That is why as certain moral issues have become political, churches are increasingly under the threat of the IRS.
No, your issue on tithing was not nerve touching. What you do with your money is between you and God. However, not everything was done away with from the Old Testament. Paul in 1 Corinthian 9 and
1 Timothy 5 states that the minister of the Gospel is to live by the Gospel. If he must, then he has to take outside employment (Paul was a tentmaker when he needed money), but that should not be where his income comes from. In
1 Timothy 5:17-18 and in
1 Corinthians 9:9, Paul quotes
Deuteronomy 25:4, which commands that the ox be able to eat as he works. This is the justification to the modern tithe.