What you can now see about Clyde's posts and his arguments are that they are not just going round in a circle but also spiraling up, setting the moral bar higher and higher in an attempt (as he he himself has conceded) to win the argument at all costs.

We've all doubtlessly heard stories from others, I can think of one where a serial rapist of students was finally fired after a student escaped his apartment screaming and putting her clothes on.

every place I've worked has had scandals involving men dating students (including teenagers)

We're talking about consensual sex between adults not rape or paedophilia.

Further examples then include, wife beating, incest and the holocaust (in a different post to the one I'm replying to). Is he suggesting that these heinous crimes are some how relevant to the situation described by the OP? At which point did the OP suggest that he was going to beat the girl up or was there somewhere in that post that he stated she was his sister? I definitely missed the part where after he beds her he indulges in a spot of ethnic cleansing.

This isn't about some Platonic form out in the ether, we're talking about actions which are "felonies" in the West, and about teacher/student relationships, all of which has been hammered out very thoughtfully and carefully, and the conclusions are practical and sound.

But these conclusions are not universally accepted either by individuals or by law makers. They are subject to debate and change. To give you a taste of your own medicine I'll draw on the example of pre-marital sex, something which you yourself have admitted to having done and to which you therefore must feel is not immoral. Yet during the 20th century many of the same US states that you have used to try and argue a legal precedent against sex with a 21 year old student (Texas, Utah, etc.) passed laws regarding fornication that made pre-marital sex illegal (many have since been repealed or are simply ignored by law enforcement). Let's be honest such laws that restrict the rights of adults in their private lives are generally made without careful and practical conclusions and do not always match the moral standards of the people that they govern.

Furthermore, are all questions of morality on a level playing field? No, every individual holds different beliefs at various levels. while you think it's ok to have sex with women you're not married to others will argue it's immoral and wrong. Many of the tactics you've used to argue against the situation described by the op could be used against you in such a debate. But does that mean that if we find a difference in our moral values on one such issue that we wouldn't find many more similarities? It's why it is rather unfair of you to bring in topics like rape, paedophilia, etc. to support your claims for this area. It gives the impression that there is some sort of universal, unchangeable criteria that covers all possible topics for debate in regards what is right and wrong and that individual is either standing on one side (good) or the other (bad). By all means pick up a history book and you'll soon see that this is simply not the case.

Stop raising the moral bar! Debate the topic itself and concede the fact that you can't win an argument over what an individual feels to be morally right or wrong. Furthermore such a debate is never going to be as black or white as the shape of the earth example that you used as an analogy.