When expressing disbelief or criticism, there are various phrases you can use instead of "makes a mockery of." One option is "ridicules," which suggests that something is being made as an object of ridicule or contempt. "Undermines" is another, indicating that something is weakening or eroding credibility. "Discredits" is similar, suggesting that something is being shown as false or unreliable. "Belittles" is another synonym, conveying the idea that something is being made to seem unimportant or insignificant. Finally, "diminishes" can be used to indicate that something is being reduced in value or importance.