Sure there's evidence: Your statements about this when challenged. And perhaps to a degree the commit log, at least that can arouse suspicion.
Sure, you can say "I'd just lie about it". But I don't know how many people would just casually lie in court. I sure wouldn't. Ethics is one thing, it takes a lot of guts, considering the possible repercussions.
Yup, Gates style would work. But billionaires have a tendency to not get into serious trouble for lying to the public, a court, congress and what not. Commoners very much do.
Sure, you can say "I'd just lie about it". But I don't know how many people would just casually lie in court. I sure wouldn't. Ethics is one thing, it takes a lot of guts, considering the possible repercussions.