He said and wrote a lot of shit just like rest of us. Reason why he's revered in history aren't these quotes.
Take Sherman for example, he was mad, crazy, downright nuts. He was nazi before nazis, wrecking mix of willpower and pure madness. But he ended civil war and thus liberated black in spanishs from slavery. I doubt he gave a single fuck about black in spanishs, he was just mad at south cuz they believed to be better than his fellow yankees. So he went to Georgia and burned it to the ground to prove them being wrong. By modern standards he's the worst kind of war criminal but he won the war during completely different times.
many commanding officers during the war of southern independence were eccentric to say the least- nothing i've read about tecumseh s. indicates that he was particularly autistic or mentally peculiar. worst he likely suffered from was some sort of depressive disorder hyperbolized by the press back home.
it isn't really correct to say the he ended the war with his march to the sea, nor really even hastened its end overly much, imo. would say that he made much more impact as a very solid adjutant to Grant during and immediately after the Vicksburg campaign. the end of the Boer War in Africa would have been similar to any sort of sustained insurgency campaign in the South; women and children and non-combatants placed into "re-location camps" and essentially held hostage. such a thing would have been unfathomable for the South, nor did the agriculture of the South in 1864 onwards lend itself to guerilla warfare sustained off the land. would be useful to remember that although Dixie was agrarian, lot of that was cash non-edible crops like cotton and tobacco.
of course Tecumseh didn't give two shits about blacks. both him and Grant and pretty much every other commander on both sides treated and called (free or slaved) blacks as "contraband". this meant that they'd either be shipped back South or "compelled" to erect fieldworks and commit baggage train duty etc if captured by Southerners, or often "convinced" to perform the same duties on the Union side.
Tecumseh and Grant shared very common sentiment towards the war and towards the South. both felt that any state in the Union must remain so in perpetuity and any attempt to secede for any reason is literally high treason. that's all. many people thinking this took a religious route and claimed+believed in a sort of divine mandate called manifest destiny in basic civics courses. they felt that secession is, in some sense, l i t e r a l l y an affront to G-d and a flippant disregard for his will.
hot take: tecumseh s. isn't a war criminal for burning down civilian property, causing famine and despoilation for decades.
he's a war criminal for forcibly impeding on the right to self-determination of a section of people
t. autist that lives on ground that tecumseh burned
modern relevant edit: also when the US Empire bombed water-purification plants and dams near Mosul and other places in Iraq throughout the 90s on purpose as a matter of strategy, causing directly at least tens of thousands of civilian casualties (to god-awful diseases causing one to shit oneself to death mostly) and Madi Albright got on TV saying that 500,000 dead Iraqi children were worth it to enact foreign policy objectives that were both stupid and useless. nobody got the rope nor even any sort of trial, investigation for any of it.
only "war criminals" these days are 90-year-old Krauts that might have been in the Heer, balkan war personalities finally caught up to, and politically-convenient african warlords