I agree do NOT confront him, it might make matters worse.
It bothers you, so its an issue, Here is what I would do. You sort of need to figure out if he looks at it alot or stumbled upon it or looks occasionaly,
This is what I would do. Tell your whole family you are installing Guard your Eyes, Everyone will monitor everyones internet use. Say it applies to you, your husband and all the kids.. Do NOT say any more.
Either one of 2 things will happend, He will stop all by himself or you will figure out how often he looks at it. If he looks at it alot, I think you will need to see a therapist more, if He stops problem solved and no harm done.