can anyone point me to the big 12 conference band rules where inappropriate use of a member institution logo is specifically called out as inappropriate?
It's actually three different provisions. Bear with me.
Article III, Section 5, Paragraph 2:
Unsportsmanlike behavior is prohibited and shall be punishable by no less than a one-game suspension and a fine of no less than $5,000.
Article II, Section 3, Paragraph 3, Subpart (iv):
It shall be unsportsmanlike to depict an opposing school's mascot, with a marching formation, costume, or otherwise, and simulate any act of ... (q) sodomy ... upon the mascot.
... and Article II, Section 3, Paragraph 3, Subpart (v):
Whether an act of ... (q) sodomy ... has been depicted shall be determined at the sole discretion of the majority of Twitter, Facebook, and other social media users.
Sounds like Tracz got off with the bare minimum punishment.