I don't see that as inconsistent at all. Why can't you be pro-free-market and anti-union? You can agree with the concept of a free market, but disagree with how unions currently operate. You appear to be confusing "I hate how unions tend to behave" with "I think unions should be forbidden".
I think unions can do great things to protect the workers they represent, but I hate that many (most?) of them seem more focused on things like retirement benefits and policies that have the effect of making it difficult to impossible to fire bad employees.
I think unions can do great things to protect the workers they represent, but I hate that many (most?) of them seem more focused on things like retirement benefits and policies that have the effect of making it difficult to impossible to fire bad employees.