Let's list the ones who ended their dealings with Texas.
a&m: Tired of playing little brother in the Big 12 they decided to... be the little brother of the SEC West. More money for the same results they were getting which is actually pretty good business if you ask me. The fact that they paint a good business decision as "we ran away from Texas because they're mean" has always struck me as odd, but aggy will always aggy.
Neb/CU/Mizzou: Escaped big bad Texas to find complete irrelevance & arguably became the worst athletics departments of their respective divisions (at least in the sports I know about). Congrats to them I guess?
That's it. That's the list. a&m is free to end their dealings with us again if they so choose, & I don't think a single SEC school would miss them should they choose to do so. I'd love it if they would come back to the big 12 to really complete the "we hate Texas because ________" vibe that y'all have going on. You could name your new conference "Fuck Texas" & your media days could just be a giant circle of coaches and ADs passing around a doll to show the world where UT hurt you. No one is shocked that you think of us as the asshole, I'm sure plenty in the Big 12 agree. Y'all can sit around and tell the newcomers stories of how you stuck it to big bad Texas that one time "x" years ago while fading into obscurity.