How many here knew that George Washington ordered slaughter of Indians during Revolutionary War?

[Sympthsical]

7. Washington would've been 57 as President

He was born in 1732 and became President in 1789.

I think if you're looking for a firm rationale, the Proclamation Line is about as close as you'll find (outside of general racism, etc). Because American settlers were violating that thing left and right. No Parliament across the ocean was going to tell them where they could and could not settle. This disobedience towards Parliament and resentment at being denied what they felt were the spoils of fighting the French and Indian War is considered one of the many root causes in the ramping up to the Revolution. Mix in that they were getting taxed to pay for that war, because Britain's budget at that point was about 60% paying off the debt incurred by the war.

They won the war, they get the land. That didn't happen, and they weren't having it.

If I have to give a decently probably accurate answer to your question, Washington was probably clearing the deck for eventual American expansion. He knew (and may have shared) the expansionist sentiments of the settlers and their antipathy towards the Natives. Hey, beat Britain and get the Natives removed from the land we fought a war to obtain? It's win-win all around.

And they may have also reach a kind of final straw moment. Until that time, various Native nations were allying or warring with European powers and each other in a delicate balance of power for going on over a century at that point. Washington fought in many of those conflicts. His views were no doubt colored by his experiences, and once in power, he pulled a kind of, "Enough already. It's ours, the end." He figured he'd resolve that pesky Native question once and for all.

Washington was remarkable in some ways. In others, he was very much an asshole.