The phrase "buy freedom of" implies that freedom comes with a price tag, which is not always the case. In fact, many would argue that true freedom cannot be purchased at all. There are many antonyms to the word "buy freedom of," including "earn freedom," "claim freedom," "fight for freedom," and "defend freedom." These antonyms suggest that freedom is something that must be earned through hard work, dedication, and sacrifice rather than simply bought. Moreover, these antonyms highlight the fact that freedom is something that is not easily obtained or maintained, and that it requires ongoing effort and vigilance to protect it.