It's not stealing, it's gaining leverage in order you get what is owed to you.
Why do you say that? Do you mean that if you're owed something then you're automatically entitled to take something else that isn't yours and you're not owed and you have no authority to take?
Or is this nice theft as opposed to nasty theft?
I don't mean to play games, and maybe it works, as did hatzflyer's 52lb weight.
But don't lose sight of the fact that it's still probably theft. Not paying someone is a civil matter. Theft is a criminal matter - no matter that it's "nice theft" - and puts you even more on the wrong side of the law than them. You'd better be sure it's going to work before going that route.