This is not black and white, is it? The person who wrote the note knows it is not black and white. But we don't want to have our friends, our loved ones, people close to us, people we respect, we don't want them going the wrong way. If we can say or do anything at all that will help them stop what they are doing, yes we do it. Now this can border on the fact that they will take out their anger and aggression on us.
Blame. Praise and blame are a pair of opposites that we are going to meet with throughout our life. All of you have heard this, some of you many times. If we get blamed, and we know it is not deserved, can we have equanimity, can we have compassion for the person speaking the blame. Do we always want praise from our friends, do we always want praise from people "we like and respect a lot"? If we are always seeking praise then we may not try to help them when they could possibly benefit from our help.
Now, there are other times that When you know a person has an undercurrent of too much anger, you probably don't want to say anything. However, it is not likely you are going to "like and respect them a lot" if that is actually their undercurrent conditioning. So, when you think about this, if you "like and respect them a lot" then they must be a pretty nice person, I hope, and in that way they will hopefully take criticism, if it is merited.
The trick here, of course, is how do you deliver say it, and that is not clear cut at all. It will depend a lot on the other person, the situation, and on the mode of communication.
To tell them that you get "afraid and angry also, and ask them to stop", yeah you can always talk about yourself to them, if you are in a close relationship where you can communicate on that level. Yet a lot of people, of course, don't share their inner feelings with others, but if you are already close to that person, you might be able to tell them, and ask them to stop.
Still, be aware of one very important thing - if you try to correct anyone else besides yourself you can run into trouble and you might lose them as a friend. It is always a gamble that you are taking because if you try to help somebody who does not want your help they might turn against you. You only have to read a newspaper long enough to find an article regarding cases where people have been verbally and physically corrected by another person, even fired from a job, and then later that person comes back and kills a few people. So, whenever you are trying to correct somebody be aware of what may happen if the person gets too angry.