You can't realistically abolish businesses. An economy of just individual tradesmen all working independently cant come close to the efficiency gains a large business has and just straight up lack the capacity for large scale projects and R&D. It's going to lead to the same outcome as your government being abolished and then businesses being reinstated.
Listed alongside the other two, the special thing about unions is they don't have this "you just straight up cant get rid of them and keep them gone" factor. So I think its completely reasonable for a person very concerned with corruption to take reform, reform, get rid of them stances respectively. Remove the institutions you can and fight corruption in the ones you cant.
You can abolish businesses too. The 2nd largest economy from 1950-1970 did precisely that, TINA propaganda notwithstanding. Chinese SOEs also serve as a model for a business that isnt really a business. It's great if you're on the central committee.
You can abolish unions as well. The results also arent exactly pleasant for the 90% of people who rely on selling their labor to survive.
But it's fucking great for that top 10% if they dont exist.
* Governments are frequently corrupt and when they are they should be reformed.
* Businesses are frequently corrupt and when they are they should be reformed.
* Unions are frequently corrupt. They should therefore not exist.
Realistically corruption is a feature of all human institutions. Unions are special only insofar as they are institutions that threaten rather than defend the wealth of the American ruling classes.