I think it's really messed up that SAHDs are seen as some kind of joke by anybody. They're going against a lot of cultural pressure to do what they do, and I think they deserve credit for that, not mockery.
My ex was sort of a SAHD for the first year or so of ds1's life. He was a furniture mover, and was low man on the roster. That meant he only got called in when all the guys ahead of him already had work (or were on vacation, of course). There were periods where he'd work as little as 4 hours in a two week period. Without my income, he'd have had to find another job, but the bills were paid, so he stuck it out and climbed the ladder. He was working pretty close to full time by the time we split up when ds1 was 7. (He got fired a few months later, but that's another issue entirely.) We considered having him stay home, but having me stay home just wasn't an option. It would have been tight even without his income...and I was making more than double what he was, most years. Honestly...until he decided that being responsible for a baby was too much stress and he just couldn't handle it (or whatever it was he thought), he was a really great SAHD, and was probably better for that than I am, in some ways...