"Taking off in the fog is a bad idea."
Nah. I take off in the fog fairly regularly, it's not all that bad. Point the nose in the right direction, take off, and climb ... Fog is usually only a couple hundred feet deep, you're through it in seconds.
Now LANDING in fog ... that I have never really enjoyed. Worst-case is landing in fog with a good crosswind (that would be you I'm talkin' about, (K)HAF) ... but pay attention to your instruments, and the approach plate for the airport you're flying into, and you'll be fine.
"I guarantee that the pilot knew that in his gut before he started down the runway."
I seriously doubt it.