That's what I'm told, but not by the IRS. It is a fairy tale, though. Small businesses cheat on their taxes in incredibly stupid and simple ways. e.g. running personal expenses through the business is absolutely rampant. I even know a guy who got a tax deduction buying a $60K engagement ring this way. This stuff is extremely easy to catch in an audit, and requires very little resources from the IRS. These business owners will always settle quickly and never fight, because they are guilty as hell and it's easy to prove.

At big corps, on the other hand, this type of activity is heavily policed and almost impossible. The idea that large corporations are rampant tax cheats is completely false. The reason that they would never dare is because the IRS has a whistleblower program where you get to keep a percentage of the proceeds, which at a big corp will be multiple millions of dollars. So any intentional tax cheating will be reported and caught immediately by employees who stand to gain more than their salary for their whole career.

The worst that a big corp will ever do is dip a toe into the legal gray areas of tax law. And in that case the IRS will be hesitant to go after them because it takes a ton of resources, and they stand a very high chance of losing. Not because the big corp has too many lawyers, but because the opposition has a legit case, unlike the small business owner who bought his engagement ring on the company card. The idea that anyone has too many lawyers for the government to handle is ridiculous anyway.

So it makes complete sense for the IRS to target small businesses and regular people and not big corps. But people don't like this because it goes against the "big corp bad, small business good" religious belief.