Sure, but just what I quoted from you leaves it as an open question which horse is the GOAT.
Every time the conversation comes up, it's really close--
ESPN picked Man O' War ahead of Secretariat, for instance, as have numerous race horsing magazines and popular sports source.
I'm not saying that's necessarily true, just that "there is no debate" is absolutely wrong when it comes down those two horses. I personally would probably would go with Secretariat as GOAT if I had to pick myself.
But it's not a no brainer, and there is certainly a debate--Man 'o' War didn't win the Triple Crown, but it wasn't even a thing at the time and he didn't bother to enter the Derby because it wasn't a big deal. He ran in iron shoes and under all other sorts of duress, and the only race he lost was because they didn't have modern starting gates and he was facing backwards when the gun went off--he spotted Upset a 4 length lead and still lost that one race by less than a half length. And he clobbered Upset in all the other races they competed in.
But Secretariat's Belmont is absolutely unreal. My mom was there that day and still talks about how that little horse just was playing a different game from the rest of the field.
But that's just one race. Overall, it's certainly a matter of debate even if you are only talking about the American GOAT--Secretariat actually lost several races throughout his career, for one thing, whereas Man 'o' War only had the one very fluky loss (and if you extend it outside the US, I wouldn't be surprised if Phar Lap, Kincsem, Frankel, and several others have their proponents).
My objection isn't to Secretariat being someone's pick for GOAT, it's to the idea that he's a unanimous undisputed selection for GOAT. And also it's kind of funny that both of the most obvious American candidates for GOAT have the nickname Big Red (which was claimed as the obvious undisputed title).