AFAIK LAV primarily taught technical shooting skills. Something he is certainly qualified to teach. I.e. how to shoot rather than if/when to shoot.
I agree with you re: public conduct but in this case his misconduct occurred after your training so you could not know what the future would hold re:LAV. What the attorneys might call “ex-post facto.”
I think it’s less that training with him could be used against and more that his compromised credibility means he would no longer be effective in testifying in your behalf.