Fat Tuesday, coming as it does the day before Ash Wednesday, derives its very meaning from the beginning of Lent. The idea is to get some serious partying under one's belt just before the forty-day ascetic run-up to Easter. So one might think the ACLU would wish to lodge a protest against a celebration so religious in inspiration. Good (contemptible?) lefties that they are, they are ever crusading against religion. Perhaps 'crusade' (L. crux, crucis) is not the right word suggestive as it is of the cross and Christianity; perhaps 'jihad' would be better especially since many loons of the Left are curiously and conveniently ignorant of the threat of militant Islam and much prefer going after truly dangerous outfits like the Boy Scouts.
The schizoid Left: anti-religious in general, but not when it comes to religion's most virulent subspecies, the fanatic fundamentalism of the Islamo-head-chopper-offers.
If you are going to take umbrage at the creation of a Catholic town, why tolerate Mardi Gras? Why tolerate a celebration which originated in a Catholic town for a purpose that is obviously tied to religion? Inconsistency, or is it the pagan excess that the ACLU types want to celebrate? We can't have prayer or a moment of silence in schools, but drunkenness and debauchery in the streets is de rigueur. Interestingly enough, in 2002, The ACLU sued when a Mardi Gras celebration in San Luis Obispo was denied a parade permit.