Why do narcissists punish those who love them ?

A narcissist is a person who suffers from low self-esteem and lacks self-respect. They don't give a damn about anyone because they lack empathy. 

They push away everyone because nobody is good enough for them or worthy to be loved by them.

You cannot give love to a narcissist because they don't need it to survive. The same as you can lead a horse to water but you can't make the horse drink it.

Narcissists are also cowards. They punish those who love them because they know they'll get away with it. You'll note they don't behave the same with everyone - because they 'know' the people who will stand up to them. But then, after a while even those who love them have enough and tell them to push off. Ask one of my kids who I haven't spoken to in over 10 years. There is only so much abuse/set ups a person will take - even a parent.

Narcissists love only themselves, if they begin to have feelings for someone, they push them away.

Narcissists don't care about anyone besides themselves.

All narcissists lack empathy which will manifest as low self-esteem. If you have dealt with a narcissist then you would know no matter what you do is never good enough. A narcissist needs an endless supply of attention, adulation, and validation. This is why they push everyone away with their self-centred and selfish behaviour. They believe they are important and entitled to everything in this world and will never stop targeting weak and vulnerable individuals.

I suggest you read this book "Unmasking Narcissism: A Guide To Understanding The Narcissist In Your Life... " by Mark Ettensahn. (2016) 

In their eyes they are protecting themselves.  They expect harm to come from anywhere, a single word can trip their triggers & all of a sudden this narcissistic is in a rage against you over one little word.  Walk on eggshells & watch every word, it is not worth the effort cause you never win. 

Who cares... So find someone new.. If you don't like how they are acting. Its plain and simple. It be a good idea to just stay friends with those types. At least until you are sure if they are like that or not. Obviously it be a bad idea and a mistake to trust someone with your heart like that and potentionally fall in love. Not a good relationship type are they. Just keep looking on the side and keep back ups planning on eventually leaving the other situation. And if its not meant to be its not meant to be.. And obviously being like that coyld very easily lead to the end. 

The basic idea is that the other person is not a valuable person apart from how that other is useful for the narcissist.  They don't even understand love, really, apart form how they can manipulate it to get people to do what they want.

Sure, they love attention, but they just move on to a new target if the recent tool is no longer giving them what they want.  That is all that others are, a tool.

Why are they like that?  That is a tougher question.  It is the way they are, by definition.  The self is what matters.  Others do not matter. They are that way for some reason or reasons, but not really obvious what makes a person narcissistic.

Narcissist personality disorder is extremely rare but diagnosing people around you with NPD is very common. 

It's the nature of the beast. Do skunks smell their own stink?  Their actions are completely normal and Narcissists have no qualms manipulating or controlling others because it's who they are. Either you learn to deal with such people or stay  away, don't expect to change them for the long run.