Jesus was quoting what people were saying about John. This can be stated without the direct quote. AT: "you say that he has a demon." or "you accuse him of having a demon." (See: [[rc://en/ta/man/translate/figs-quotations]])
This can be translated as an indirect quote. AT: "you say that he is a gluttonous man and a drunkard ... sinners." or "you accuse him of eating and drinking too much and of being ... sinners." (See: [[rc://en/ta/man/translate/figs-quotations]])
If you translated "The Son of Man" as "I, the Son of man," you can state this as an indirect statement and use the first person. AT: "you say that I am a gluttonous man and a drunkard ... sinners." (See: [[rc://en/ta/man/translate/figs-quotations]] and [[rc://en/ta/man/translate/figs-123person]])
This appears to be a proverb that Jesus applied to this situation, probably to teach that wise people would understand that the people should not have rejected Jesus and John.