Left parties say observe Dec 6 as `Defend Constitution and Secularism Day': New Delhi, Nov 24 (UNI) Six Left parties led by Communist Party of India (Marxist) on Saturday appealed to the people to observe December 6, which coincided with the 26th anniversary of the demolition of the Babri Masjid, as `Defend the Constitution and Secularism Day'' in defence of secularism and democracy in the country.