There also is nothing wrong with proprietary software. Don't run it, or purchase it if you have some moral disagreement with it, but many people don't and are perfectly happy to pay money for it.
There are a lot of people who believe there is something wrong with proprietary software. You don't have to agree with the FSF or their goals, but it does everyone a disservice to conflate the argument for software freedom with an argument against proprietary software. The FSF considers commercial use and distribution of software to be an important part of software freedom and does not consider licenses that forbid it to be free.
And if you think it is unethical to sell proprietary software and refuse to use it oneself, it is also perfectly reasonable to advocate that others follow the same course. A value position that one doesn't believe others should follow isn't a value, it's just a preference.
There's absolutely things wrong with proprietary software. It leaves software users in the position of having technology that they cannot control freely. See, e.g. the arguments from GM and John Deere that you do not have permission to modify your own car or tractor. Or countless other examples.
And basically zero of the people who pay for proprietary software are saying "I'm so glad this is proprietary". They pay because the package of what they get in utility is worthwhile and outweighs any concern about the proprietary nature of the software.
