Canadian citizens carrying diplomatic or official (Special) passports DO need a visa to visit Mexico for official or tourist purposes.
The requirements to apply for a visa are:
2. Valid diplomatic or official passport and a photocopy of the page containing the photograph and personal data.
3. One photograph measuring 3.9 cm x 3.1 cm, face uncovered, no eyeglasses, frontal view, in color and with white background.
4. Diplomatic Note from the Department of Foreign Affairs and International Trade Canada (DFAIT) requesting the visa and specifying the purpose and length of the visit to Mexico