What does Genesis 19:7 mean?

Lot is attempting to save two traveling strangers staying with him from a violent mob of men who have surrounded his house. These men—all the young and old men of Sodom—are intent on gang raping the visitors. Lot does not yet seem to know these two visitors are actually angels disguised as humans, nor that they have come to investigate Sodom's sins in preparation for God's judgment on the city. Still, the culture of the day demands that good men protect those to whom they have offered shelter. In fact, Lot's motive from the start seems to have been to protect these strangers.

Lot has gone out of his house to address the mob, closing the door behind him. He begins by calling them brothers, acknowledging his relationship with them as a leader of their town. He begs them not to do such a wicked thing, which removes all doubt about the meaning of the crowd's demand in verse 5.

Next he will offer them a terrible alternative.