Thanks for asking. The thing about Genesis 19 is that it is providing a picture for us, in parable sense, of the times towards the end of the church age. That is why Jesus referred to Lot coming out of Sodom (in Luke 17) as a picture of the contrast between true believers and the fallen congregations at a later time, not just at the Genesis time of the Genesis story: "Likewise also as it was in the days of Lot; they did eat, they drank, they bought, they sold, they planted, they builded; But the same day that Lot went out of Sodom it rained fire and brimstone from heaven, and destroyed them all. Even thus shall it be in the day when the Son of man is revealed."
As we we think about this, it is the city Sodom which provides a picture of the fallen congregations of the church age. Eating and drinking and buying and selling and planting and building are all spiritual terms describing, in parable form, the activities of the congregations of the church age. People eat and drink the body and blood of Christ, and merchandise in the souls of persons, and plant and build 'churches' and so on. In contrast, those inside Lot's house are a picture of the true believers as the church age winds down. The term 'angels' in the Bible simply means messengers and is used to describe true believers often, and the term angel of the Lord and simply angel can even refer to Christ. True believers are God's messengers (angels). (Incidentally, these angels are referred to as men in Gen 19:10). The people of Sodom want to "know" the true believers but they only want to do so in order that they can abuse them or treat them wickedly, as Lot says. It so happens that God 'knows' his true believers in the Bible, his own sheep. This is not really a sexual 'know'. It is God knowing in a spiritual way his own sheep because they are of him spiritually speaking. It is not for the fallen congregations to 'know' the things of God or to be known of God, since they only have evil in their hearts towards God. I would not think of the term 'know' in Genesis 19 as being so much a sexual reference as what is implied by the parable meaning, to know spiritually. Thus, Lot refuses, because of their wicked intent spiritually. The terms "which have not known man" and "sons in law, which married his daughters" are loaded terms with spiritual meanings in relation to Christ. The sons-in-law seem to have trouble heeded Lot's warning and it seems to them that he is mocking them. They also do not get mentioned again as ones whom the angels take out of the city. Anyhow, if you are focusing on the surface story, as being one about physical sex, I think it should be taken more as one of spiritual knowing rather than physical. In like manner, the blindness that is inflicted on the city of Sodom by the messengers of God should be looked at as ultimately not pointing to physical blindness but to the spiritual blindness that the congregations of the church age have as the church age draws to a close, and how they weary themselves trying to find the door (which is a parable word for Jesus).