I've been following this thread because the original question got me wondering about how taxes are calculated and why various methods of stimulating the economy supposedly work. I'll try to avoid any opinions on whether any of those methods work and just give things as I've researched and as makes sense to me.
I started off by looking into the regulations on taxes for businesses. The first relevant and readable article I found was
this, which is a bit old. Even at a bit old, it probably gives a decent idea of how things are because I don't think the tax laws have changed much except for the amount owed. It seems that the tax is indeed based on net income, which comes after subtracting out things like wages and materials or other business expenses. So my understanding is that since the workers have their income taxed directly and sales of items are often taxed directly, they don't tax the business again for those expenses. So the shareholders or owners of a business are the ones who are affected by tax increases on businesses.
Now as for how cutting those taxes, or at least raising them less, is supposed to help the economy, I'll turn to my own logic rather than an outside source. America is a capitalist country. That means that people can earn different wages for different jobs and except for setting a minimum wage the government doesn't have much say in what a person should earn. Obviously people want to earn more and they work for that. Some people manage to do it and some don't. I don't even want to think about going into the reasons why that happens but it does. The people who do get to the top are often in positions of hiring other people and deciding how much they make. Now remember, those people in charge are driven by a desire for more money. At least most of the time. So if they find that they are making less money because the government takes more of the money they make, they will start to look for ways to reduce expenses while still making income so they can get the same amount of money into their pocket. If they cut a worker and still hold productivity, now those wages go to the owner or shareholders instead of to that individual. It is now taxed at the higher rate for the company instead of the individual but it is still more money in the owner's pocket. I think that is the logic behind not increasing taxes on business owners to help the economy. If the taxes stay the same or are lowered, they are not guaranteed to hire more workers. But if they have extra revenue they will be more likely to look for ways to turn that money into more money. If they are getting less money they will look for ways to offset it, and often that means someone else loses out.
Maybe my logic is flawed. Maybe I'm a bit pessimistic about humanity. But that makes sense to me. I hope it avoided any of the political leanings that this topic is almost guaranteed to bring out.