Minecraft – My villagers are leaving the village

For some reason, this has been changed to a slider with only two settings. You can see the slider in the Options menu, labeled "Difficulty":

Moving it all the way to the left turns on Peaceful mode. I confirmed this by going out in the dark, walking up to a skeleton, and then flipping the slider all the way to the left: the skeleton disappeared.

There's no visual feedback as to what difficulty setting the slider's two positions are, which is a UI fail on Mojang's part. But seeing as this is the first Alpha release with these new menus, it will probably improve.

Because you accidentally attacked a villager or two, your popularity in the village is probably low enough that the Iron Golems will attack you on sight.

One option is to prevent more Iron Golems from spawning, and then killing any remaining ones aggressive towards you in the village. You should theoretically be able to prevent them from spawning by either reducing the village population to fewer than ten villagers, or by reducing the number of homes (a home can be removed by deleting the wooden door—the structure itself does not need to be demolished) to fewer than 21.

Once you have prevented the Golems from spawning, you can attempt to increase your popularity with the villagers, to prevent any golems that spawn in the future—because of population increase/home construction—from being hostile. The only way I know of to increase popularity with villagers is to trade with them, specifically for their last item (related Arqade question).

Another option, if you don't care about the village at all, is to wipe out the village's population, resetting your popularity for that village.

Disclaimer: I have not tried the aforementioned solutions myself, so I cannot guarantee they will work.