Maybe a careful way to push users would be this?
- If the user is accessing the wizard with HTTPS, silently enable the setting. HTTPS is obviously working.
- If the user is not using HTTPS, ask him to try it out – click here to switch to HTTPS, if this doesn’t work out, come back here and click skip. If this works, congratulate him and enable the setting. If it doesn’t, leave it be.
(For extra points: If the user doesn’t have HTTPS set up when the wizard exits, seed a system topic in the internal category with instructions for setting up HTTPS.)