Yes, most are. If a Muslim girl has a relationship with a 'western' boy, this is not allowed and has led to so called honour killings. Or even something as trivial as wanting a career. Non religious cases do exist but in general it is a religious thing.
I do get your point but you must be willing to accept that it's a very small minority of such things that cause the situation to escalate beyond simple family arguments? I've been to 3 weddings in the last decade between muslim women and white non-muslim men, in every single case their family were there and two of them even had the local Imam giving a blessing. A good friend of my wife's is a right party animal girl, bordering on the stereotypical Essex girl image, yet she's a proper daddy's girl with her dad, a very strict muslim who wears the full kit all the time including massive beard. Most are in the middle of this though, families might not want their muslim daughters going off with white men but most accept it after the arguments cool down.
Yes, there are undoubted and utterly unacceptable cases of pathetic individuals trying to protect their "honour" and they rightly get the treatment they deserve in our country. In some of the cases I've seen, it's naturalised immigrants who do the crimes, my view is that they should be made to serve their sentence in the UK then deported back to their country of residence after having their adopted nationality revoked. It works quite well in the US most of the time, even though it's caused some genuinely unintended consequences, their view is though that a crime is a crime and if it fits their standards of unacceptability then you're shown the door regardless of how long you've been there.