When you love someone, you send them positive, beneficial energy.  I don't thing anyone would question that.   When you have negative emotions like anger, you also send energy to those involved.   If you get angry at others, you send negative, harmful energy toward them.  This energy can weaken the person resulting in illness.  
    Some may think that it is good to send negative energy to those who anger you, but there is a catch to this.  Actually two.   When you send out negative, harmful energy, some of it goes right back to you and harms you also.  Also, though the other person is not consciously aware that you have sent them harmful energy, unconsciously they are and unconsciously, they may return the favor.  So anger harms you as well as the one you are angry with.  
    Another reason for us to try to control our anger.  I know it isn't easy.  I'll get angry at my dogs when the see a cat and take off after it pulling on my arms when they get to the end of their retractable leash.  But, with practice, I've learned to quickly flush out that anger and replace it with understanding and tolerance and by just reminding myself that I love them, even when they do something I don't understand or approve of.   I get angry when another driver cuts me off on the highway or changes lanes in front of me fifty feet from a red light.  Again, I quickly release that anger by trying to understand that some people are so controlled by egotism, they can't stop behaving like that.  In short, we all need to learn to be more tolerant and forgiving because our anger harms us as well as others.