Same as you would march against any other similar Instance.Actually many protests in our future (as well as it was in the past) and all around the world will be against company's and transnational cooperation's (rather then local regimes and varieties of paravans of control) because they are the ones deciding, limiting, installing controling not the politicians or the government's...
...anybody who thinks that political party in power or the president of the state (with associated hierarchy) really represent people or that they are making any serious decisions is not really aware of anything what is going on today and how the "machine" works.
Its not like people really have that choice, nor does societies today encourage or provide opportunities to choose from any alternative... new generations only have illusion of that choice which you speak about and if you dont see that then its understandable why you wouldnt ...its not in the interest of the biggest coorp. to allow let alone provide alternative .. why would they ?g and understanding why it have nothing to do with Democracy the better... with time mediocre people would soon follow and understand as well eventually.
It seems you are only projecting this company to be 'Evil' as a defence mechanism.
I've never heard of a limited company or coorperation that doesn't work for profit. They all exist to make money. This can be done be either producing products effectively (Cheap labor, Genetic modification etc) or making people think they are 'trying to save the world'. Companies will ALWAYS choose the route that brings them the most money, and one single company can't be blamed for this if you don't approve.
How far a company are allowed to go to make money is regulated by your government. If your government fails, vote for another party. If that party looses, the public mind has spoken and decided that your country overall wants to keep GM food. If your company wins but lies, they won't stay in office for long in a wellrun democracy.
You say that the companys control your government, this is impossible in a democracy unless they are fixing your elections. The people control the governments and if they don't approve the government will be kicked out by next election because only people can vote, not companies. You never have to compromise, you can always vote for a party which you approve or start your own party.
If this is not the case, then the problem does not lie with the company in question, but with your government and political system. If it is as you imply, that companies now control governments, you should be out there demonstrating and marching against the concept of democracy, not the company.