How come nobody sugggestedsuggested dämlich? It fits in all the examples too.
edit: Dämlich has the (to me at least) literal connotation of "like a foolish old lady", which is unkind to old ladies, I know. Entirely subjectively I would say it is probably just a tick more negative than albern, slightly in the direction of "anyone who does this must be a bit stupid".
Anyway:
He keeps calling you these silly names. (playful)
dämliche Namen, perhaps he's trying to make you look stupid, or he's making himself look stupid.
Your silly husband is participating in the brezel marathon. (irresponsible)
Dämlich is exactly right here. He's daft to contemplate it.
That silly man will never graduate. (unintelligent)
This isn't something you would say in English either, I think, but here dämlich could mean "too scatty" otor "too unorganised".
Parse HTML with regex? That's a silly idea! (foolish)
Now here dämlich is right, meaning "it's a stupid thing to try".
Dämlich is used a lot, but could be construed as a faint insult when used personally.