Are there any weak hadiths in Imam Malik's Muwatta, and how can one convince a person who is bigoted about the Muwatta and sees it as the sole reference?

"Al-Muwatta'" is a great book, praised by Al-Shafi'i before Al-Bukhari and Muslim, and Ibn Kathir considered it among the most beneficial books. Scholars have given it great attention, however, it contains weak, mursal, and disconnected hadiths, and balaghat (reports) whose origins are unknown.

As for the common person, he must follow the people of knowledge, as Allah the Almighty says: (So ask the people of the message if you do not know). He is not obligated to follow a specific madhhab. Whereas one who is capable of deriving rulings acts according to his own ijtihad (independent reasoning), and it is not permissible for him to blindly follow in matters where he believes the truth to be otherwise. The fanatical person should be advised to seek knowledge and abandon blameworthy fanaticism, or to follow someone he trusts among the people of knowledge.