The Natives of the so-called 'New World" helped the Pilgrims survive their first brutal winters in the Plymouth colony.

From Wikipedia:
"Americans commonly trace the Thanksgiving holiday to a 1621 celebration at the Plymouth Plantation, where the Plymouth settlers held a harvest feast after a successful growing season. Autumn or early winter feasts continued sporadically in later years, first as an impromptu religious observance, and later as a civil tradition.
Squanto, a Patuxent Native American who resided with the Wampanoag tribe, taught the Pilgrims how to catch eel and grow corn and served as an interpreter for them (Squanto had learned English during travels in England). Additionally the Wampanoag leader Massasoit had donated food stores to the fledgling colony during the first winter when supplies brought from England were insufficient.
The Pilgrims celebrated at Plymouth for three days after their first harvest, in 1621."

In return, over the next 4 centuries, the White Europeans / Americans deceived the Natives, took their lands away from them, enslaved them, consciously committed biological warfare on them, killed them, massacred them, and committed GENOCIDE on the Natives, over 500 Tribal Nations.

The Natives treated the Pilgrims with Kindness andcompassion. The White Europeans, now Americans repaid them with treachery and deceit, atrocities, massacres, and eventual GENOCIDE.

This practice of celebrating 'Thanksgiving" is an insult to the Native Americans, an insult to our intelligence, and more especially, an insult to our humanity and COMMONDECENCY.

If anything, the 4th Thursday of November should be observed as a day of MOURNING...
a day of SHAME,
a day of INDIGNATION... 
instead of celebrating it with parades, travel, shopping, and other ignominious activities.

This petition is important because it will bring back and strenghten our sense of humanity and common decency, as well as our sense of justice, liberty, and equality.

http://en.wikipedia.org/wiki/Thanksgiving_(United_States)