So maybe the evidence is with you and I'm not remembering Rabbi Mizrachi's position right possibly. It says that the thought is worse than the sin with immodesty, because the sin is one time say 8 rounds x30min-1hour and it's over, the thought can go on and on for years. If it is forbidden to do the act, it is, then the thought is forbidden too. I know from painful experience that every blessing has an equal opposite curse if you refuse it, so if it is a blessing for Noachides to be modest, it is, then it brings an equal opposite curse to a life of love and children to be immodest. Even if we G-d forbid forget all the laws, it is enormously in one's self-interest to keep one's thoughts clean.