One of the most profoundly difficult things we are asked to do in healthy relationships/friendships, is 'Sit in the Fire' when your friend/partner is feeling angry.

As long as they do not insult or demean or physically harm you, the most powerful and effective thing you can do is, breathe, ground and stay present... empathise.
Do not give advice, unless clearly asked for.

Feel the feelings of wanting to run away, or make it better.
Keep breathing and stay put. Sit in the centre of the heat.

And remember, in all likelihood, (unless they really ARE an abuser) ...their anger is a valid response to things that only they know about... until you fully listen.

Leave your fear and judgement at the door,
and empathise more and more.

If it feels safe and appropriate, and you are in the same space, see if you can stay, or get back in physical contact.

Anger is an incredible self-protective emotion...and wonderful learning and healing comes from staying present and hearing them out. If done well, it can DEEPEN the intimacy and trust in the relationship. But if not done well, it can do the opposite.

SIT IN THE HEAT.  ( but don't put up with abuse.)

Ultimately all communication is about building connection and relationship. Even when it is just a sharing of facts and information, the relational brain/being is tracking for safety and connection by being understood.

1. BE PRESENT  - put your full attention on the other - step into their shoes.

2. FEEL AND SHOW EMPATHY with your body language and/or words - To do this authentically, you need to put your attention fully on the other, to feel like you are literally stepping into their shoes.
“Wow, I really get what you are saying!”
or
"That must be so upsetting/confusing/lonely/disappointing for you!"
​"I'm so sorry to hear that."
Mirror their tonality. If they sound upset, you sound upset. If they are excited, be excited. And if you are truly stepping into their shoes, this will be an authentic response, not fake or made up.
      
PS you can try to fake empathy, but most people notice, and it doesn’t work for very long.  

3. BE CURIOUS. Ask clarifying questions to take the speaker further.     

4. ADD TO THE SUBJECT. "Yes, and... " Stay on topic and add an interesting nuance. But don't talk about you…. yet…. your time is later when the speaker has been reasonably listened to.  

5. DO NOT INTERRUPT.  Or at least be mindful of when to interrupt. Interruptions come in many forms. From overly enthusiastic agreeing noises... to not letting the speaker finish a sentence, a paragraph, or an idea... to constantly bringing the conversation back to yourself.  Doing this builds resentment and disconnection. 
​
Research has shown that the brain interprets constant interruptions as a form of minor trauma. Similar to, but not as bad as, constantly waking up during the night. And we all know what that does to your state of mind.  And any form of trauma ie Complex PTSD etc, can make someone highly sensitive to interruptions.

5. BE PATIENT. SLOW DOWN. BREATHE. IT'S YOUR TURN SOON. No matter how how hurtful or 'wrong' your partner feels to you, don't react, don't fight back, don't escalate. You are building the relationship, which, ultimately,  is more important than the subject matter you are discussing.

6. DON'T GIVE ADVICE - unless requested. This is a hard one for caring, and especially practical people. It's often their way of showing love and support.
However, unless asked for,  giving advice is unhelpful in 3 ways.
a) It assumes the other person doesn't have solutions for themself. - ie it's diminishing of their capacities.  If you listened longer, or asked what solutions they have already tried, you might find they already have a solution. 
b).  If you haven't done a whole lot of empathising first, then your advice is likely to fall on deaf ears.  You might even end up with the original speaker being very upset with you. And all you were doing was trying to help!  ;-) 
c). Paradoxically, it puts you in a power-over position. You can feel stronger and wiser as you dispense your pearls of wisdom which can distract you from being PRESENT and EMPATHISING which are much more important than your advice. Unless asked for ;-)

CAVEAT
Unless explicitly stated, all communication needs to be reciprocal. A flow of give and take between speaking and listening  If you are a Generous Listener, there is no doubting that people will like and appreciate you. But be careful that the relationship is not just one way - ie you listening and them speaking. Obviously , this can become very unsatisfying, very quickly.
​
After a decent period of generous listening, it can be a good idea to insert a few thoughts and ideas of yours, and see if the other person can pick them up and also become a Generous Listener. If they reciprocate in this way,  you can end up having a balanced give and take of listening and sharing…. and ultimately deepening the TRUST in the relationship.