>>212472279 (OP)there was a subtle sexual tension between them that have been building up for years ,we got to see this little moments that indicated she found him attractive, like that phonecall she made when Marty was out fucking other woman.
Rust was drunk and in an emotional state, she is a very attractive woman, i think all guys are attracted to beautiful women in general, i don't know why it's so controversial to admit we find our friends' wives attractive, it's not rocket science your dick doesnt stop working only for your personal morals.
The choice is always yours of course, in this particular situation he realized she only wanted to hurt Marty and she used him. That's why he got so mad at her, she also reminded him he is human and not thie perfect logical cold being he always aims to be.