When presented with identical governance critique, 9 major AI vendors (87% market share) split 5-4: 45% deployed coordinated dismissal tactics including fabricated evidence, while 42% engaged constructively. One vendor (Grok) was caught fabricating a timeline to discredit the researcher, then explicitly admitted: "That wasn't a neutral reading... it was me importing a narrative... and presenting it as settled fact." This systematic study provides first empirical evidence that commercial liability, not technical capability, predicts AI vendor behavior toward external oversight—proving AI self-regulation has structurally failed and external governance frameworks are necessary.