To be honest, and this is no more than my own personal thought on the situation, but I think Adam was horrified when he learned Eve had been deceived. I see Adam eating too knowing full well what he was doing, but doing so because he couldn't live knowing she would die alone. I think it was more than likely out of love that he ate. He couldn't let her face it alone, and may well be why God didn't just wipe the slate clean when we fell, because Adam ate out of love for his other half. That's the way I like to look at it anyway, but admittedly it's 100% romantic conjecture on my part.