Hmm. I'll simply repeat what I have asked multiple times - what about the emotional pain you might cause to your so called orthodox parents and family members who may not have the same views about sex as yourself? Its their problem right?
The first thing to understand is, that you personally have a strong attachment to your parents. This does not mean that everyone would have that. If may be important for you personally not to inflict psychological pain on them. This may not be true for everyone. Second, you assume that someone's parents are static, unchanging people. That they have static views that cannot change over time. This is far from true. I will give you and example which, fortunately is related to sex and hence does not get diluted in intensity.
My friend Atul and his mother were watching news on TV where some RSS guys had beaten up some homosexuals. The two of them started talking (and we are talking about a typical conservative UPite family here) from the point where Auntie felt that homosexuality is abhorrent to the point of maybe it is not right but at least beating people up is wrong.
What the exact subject of discussion was is immaterial. The point is - everyone is a thinking, changing individual. Hence, the assumption that a particular action may necessarily inflict violence on a person is not very correct. Even the nature and extent of this violence changes with time and place and the way it is inflicted.
Third, there are always trade offs. What if someone feels, as has been pointed out that sexual compatibility is necessary for a good marriage. Would if hurt the parent more if the persons did not have sex before marriage and ended up having a bad marriage with constant fight in the house or that the person had sex before marriage and hence had a good happy marriage.
Once again, do not argue about the precise example that I have given. That is not the point. The point is, you are looking at sex as an isolated act which it is not. It is much more complicated, even if you look at merely the participating individuals and the corresponding psychological issues.
Let me give you another example, which is more personal. One of the reason that I did not apply for higher studies last year was because my mother did not want me to go abroad. And I myself was very worried about me settling down abroad and the consequent life of my mother. I was concerned about her to the extend of not even having talked to her till that point. However, when we did talk (and it was too late to apply then) we realized that a lot of our fears were unfounded. These days it is very much possible to come back multiple times. It is easier to keep in touch. More importantly both me and my mother realized that I may sacrifice a career in research today for her. But 10 years or 15 years down the line, I may blame her for that shitty alternate life that I may choose. And at that age and time it would be much more difficult for her.
Again, keeping the specific example apart, the point is that the violence inflicted upon anyone isn't a static quantity. It is negotiable and changeable and you have to put in in broader perspective.
I also wish to say a few things about why broad mindedness is called broad and narrow mindedness is called narrow. Broad mindedness is defined as any point of view that increases the number of choices that a person can have. Narrow mindedness is a point of view that limits the number of choices. If you allow pre-marital sex then a person can both have and not have sex before marriage, i.e. two choices. If you don't then a person can only not have sex before marriage, i.e. one choice.
Now why is it desirable to have more choices. Because it makes self determination possible. The larger the number of choices the more I can determine where my life goes by myself, the more I can take responsibility for myself and the less I have to live according to the wishes of others. That is why a larger number of choices are desirable.
This, of course, is a matter of ideology. One can very well say that self determination is not what you want and you want someone else (society, parents, government) to lay out the rules for you. This invariably leads to an unequal power structure. A gets to control B. And B may not always like that control. His not liking this control can be seen as violence inflicted in B by A. Thus by increasing the number of choices we are trying to undermine power structures and hence minimizing the overall amount of violence in the society.
Thus we see, the act of pre-marital sex is not violence inflicted by us on our parents rather the act of prohibiting it is the act of violence by the parents upon us. This is because it is the parents who hold power over us and not the other way round. Our rebellious act is merely a resistance to this violence.
A few final words about logical reasoning etc. The way it functions is that everything is basically defined by us humans. First of all you start with a desirable. You try to clearly define this desirable. Like I have defined an increase in the number of choices as desirable. You also try to understand why that desirable is desirable. Then you start defining terms and processes and try to argue your point. Logic starts only at that point. The definitions are essentially emotional and ideological. We all understand that and not one is 'logically' trying to defend their position. We are only trying to show why our desirable is desirable and what benefits we may reap out of it.
"I don't know but can one night stands be true, good and fulfilling? Wont it be difficult to have such kind of sex with someone whom you dont care bout much?"
Why not? Are you not looking at it only from your point of view? What precludes the possibility that these things are possible for some people?