A couple of years ago the NY Times published an eye-opening interactive chart showing the actual tax rates paid by S&P 500 companies: http://www.nytimes.com/interactive/2013/05/25/sunday-review/... (Related article: http://www.nytimes.com/2013/05/26/opinion/sunday/who-will-cr... )
Regardless of whether you think corporate income taxes should be higher or lower, it's dysfunctional to have a system in which large companies and super-wealthy individuals can avoid paying headline tax rates but small companies and individuals don't have a choice.
The IRS, understandably, wants to stop this charade.