Honour Killings have no basis in Islam
These are done by people with no understanding of Islam and fixed ideas based purely on UnIslamic culture.
For example, they will kill a girl because she did NOT marry her cousin.. or she wanted to marry someone else (even if that is a Religious boy from another village) etc
There is no honour in this, infact, it is a big sin. It is murder.
These things actually come from UnIslamic pagan practises, particularly in India and Pakistan. They are just like the Sikhs and Hindus who believe in Caste systems, who treat women in evil way. -- For example, they will think that women have to walk behind the husband, that after the man's death women are of no use. Infact, it is a practise of the Sikhs to burn the man's wife after he has died. This is called practise of Sati.
In some parts of the Middle East and Africa, there are also so called honour killings.
None of these are from Islam.
People, should treat one another with kindness and respect. They should seek to find the real Islamic solutions rather than one contrived by dirty unkempt tribesmen or mystics who dont know anything about Islam, but are percieved as holy men.
Unfortunately, all this is a product of people being away from the real core beliefs in ISlam, such as Tawheed. You will find many of those areas rife with Shirk (Associating partners with Allah) and bidah (innovating new ideas and rituals into Islam). They have built so many shrines to the dead, they do so many odd things such as drinking dirty water from some shrine and calling it Zamzam astaghfirullah, or these same Sufi/ignorant people believe that deformed children are "rats" sent by God and can heal people!!! You can read more about these stupid supersticion here:
Sufi Saints and the Rat Children of Pakistan --
http://news.bbc.co.uk/1/hi/world/south_asia/122670.stm
it is suprising that people dont realise how evil they are.
So, when there is no understanding of Tawheed / Aqeedah, the most important things for a Muslim, then there will never be any good!! and Muslims will always be weak and have bad leaders. Once we change from the basic foundation, and work up, by following the Quran and Sunnah, Allah will give us the strength and power again, that the Muslim Ummah has lost due to these Shirk and Innovations.
Please see following very important articles
Fundamental Beliefs in Islam Tawheed and Aqeedah
Importance of Tawheed in Reviving the Ummah
Why Muslims are Weak Today
The Current State of the Muslim World
wasalam.