I just did a quick search where I expected to find the original article I saw on this that reminded me of this recently, but can't figure out who shared it. In searching I did come across a similar telling of the story, though the overall article is making a different point on the issue:
"It was the Wampanoag in 1621 who helped the first wave of Puritans arriving on our shores, showing them how to plant crops, forage for wild foods and basically survive. The first official mention of a “Thanksgiving” celebration occurs in 1627, after the colonists brutally massacre an entire Pequot village, then subsequently celebrate their barbaric victory. "
This is from this article which goes into much more depth about how the holiday actually evolved after multiple attempts to get it off the ground.
This source also makes reference to the same genesis of the first use of the term, though not the first official holiday celebration within the continuous line of the holiday.
I totally see your point in only celebrating (or choosing not to) the genesis intentions of a holiday. This one seems to have some controversy over its genesis story.