This is about determining the best team. I mean, what’s the practical reason to not allow 9-3 Mississippi St. into the tournament? Sure, they have shown on the football field that they don’t belong, but what’s the practical reason to not just let them in and give them a chance?
That sounds ridiculous to you, doesn’t it? But it’s basically your argument, only you’re promoting teams from much worse conferences.
And, by the way, we haven't even gotten to a scenario where 2 or 3 small conference teams are undefeated, or have one close loss. At some point that's going to happen.
“It hasn’t ever happened yet … but it could” is an incredibly weak argument, especially for a guy looking for practical arguments.