Marriage in Islam: Sex, forbidden subject?

Sex is considered a forbidden subject for some of the so called "Religious" Muslims and even for other religious people of different religions! Somehow is looked at with a disgraceful look! Faces change when they hear that word! Why? What's wrong with it?

In Quraan the holy book of Muslims, sexual related issues are discussed in more than one occasion, the word "Nikah/نكاح" which means "Sexual Intercourse" is mentioned several times explicitly! So what's the deal?

I think there's nothing inherently evil or bad of itself, sex is no different here. True, prostitution is bad but not sex itself! Immodesty is bad but not beauty! Can't we differentiate?! The knife is bad if it will be used for killing but it's a handy tool otherwise!

So what does Islam say about sex?
Sex and erotic interactions is a natural right for males and females that can only be obtained through marriage. I think that's why in Quraan Allah calls marriage "Nikah" (sexual intercourse) because it's the unique feature the marital relationship has than other relations.

Herein a nice demonstrative story from Quraan about sex:

A little background: The Arabic man in pre-Islam era if he says to his wife "You are forbidden on me like my mother" he will never have sex with her thenceforth, that's called "Zihar" they remain married but no sexual intercourse.

During the Prophet time a Muslim man had an argument with his wife and said that phrase to her. The wife went to the Prophet to complain about her husband that he wouldn't have sex with her anymore. Then Allah revealed to his Prophet a whole Surah (chapter in Quraan) about this occasion which is called "Surah Al Mujadila":

"Allah has indeed heard (and accepted) the statement of the woman who pleads with thee concerning her husband and carries her complaint (in prayer) to Allah: and Allah (always) hears the arguments between both sides among you: for Allah hears and sees (all things).

If any men among you divorce their wives by Zihar (calling them mothers), they cannot be their mothers: none can be their mothers except those who gave them birth. And in fact they use words (both) iniquitous and false: but truly Allah is One that blots out (sins), and forgives (again and again).

But those who divorce their wives by Zihar, then wish to go back on the words they uttered, (it is ordained that such a one) should free a slave before they touch each other: these are ye admonished to perform: and Allah is well-acquainted with (all) that ye do.

And if any has not (the wherewithal), he should fast for two months consecutively before they touch each other. But if any is unable to do so, he should feed sixty indigent ones. This, that ye may show your faith in Allah and His Messenger, those are limits (set by) Allah. For those who reject (Him), there is a grievous Penalty." Quraan 58:1-4

قَدْ سَمِعَ اللَّهُ قَوْلَ الَّتِي تُجَادِلُكَ فِي زَوْجِهَا وَتَشْتَكِي إِلَى اللَّهِ وَاللَّهُ يَسْمَعُ تَحَاوُرَكُمَا إِنَّ اللَّهَ سَمِيعٌ بَصِيرٌ

الَّذِينَ يُظَاهِرُونَ مِنكُم مِّن نِّسَائِهِم مَّا هُنَّ أُمَّهَاتِهِمْ إِنْ أُمَّهَاتُهُمْ إِلاَّ الَّلائِي وَلَدْنَهُمْ وَإِنَّهُمْ لَيَقُولُونَ مُنكَرًا مِّنَ الْقَوْلِ وَزُورًا وَإِنَّ اللَّهَ لَعَفُوٌّ غَفُورٌ

وَالَّذِينَ يُظَاهِرُونَ مِن نِّسَائِهِمْ ثُمَّ يَعُودُونَ لِمَا قَالُوا فَتَحْرِيرُ رَقَبَةٍ مِّن قَبْلِ أَن يَتَمَاسَّا ذَلِكُمْ تُوعَظُونَ بِهِ وَاللَّهُ بِمَا تَعْمَلُونَ خَبِيرٌ

فَمَن لَّمْ يَجِدْ فَصِيَامُ شَهْرَيْنِ مُتَتَابِعَيْنِ مِن قَبْلِ أَن يَتَمَاسَّا فَمَن لَّمْ يَسْتَطِعْ فَإِطْعَامُ سِتِّينَ مِسْكِينًا ذَلِكَ لِتُؤْمِنُوا بِاللَّهِ وَرَسُولِهِ وَتِلْكَ حُدُودُ اللَّهِ وَلِلْكَافِرِينَ عَذَابٌ أَلِيمٌ

المجادلة - الآيات ١-٤

There are many morals out of this story but in regard to this topic, it shows how significant, yet normal that right is for women and men equally.

I'm not advocating for immodesty by talking about sex senselessly but rather advocating for sex education. It's unarguable that sex is one of the most important elements of the marital relationship, not only that but it's the unique feature that distinguishes marriage from other relationships, so neglecting it means neglecting a huge part of the relationship which off course means a huge problem in the relationship! :^)