Well, when you put it that way...
Yeah. I think he was at his most "lunk-headedness" during ATAI. First, the stupid "that was my barber" line. He'd already made up his mind to tell her. Why would the phone call make him change his mind? Then, we have the conference room conversation. Lois is so clearly hurting. Not telling her the truth at this point was beyond being a lunkhead. It was plain cruel. Next, when she catches him stealing the jewels. Again, the perfect opportunity to tell her the truth. (Lois' acceptance of his "my parents were kidnapped" excuse never sat right with me. I always thought she should have questioned that. At the very least, asked why he hadn't confided in her.) Finally, proposing without telling her the truth - definitely a lunkheaded thing to do.
Of course, I blame the script writers, not Clark! That's why I enjoy reading fanfic so much.
- Vicki