I have never understood why people ignore, avoid, or stay angry at a friend for something they’ve done, or worse, stop being their friend. If your friend makes a mistake, does something they regret, or doesn’t understand why what they did is wrong, then holding a grudge against them or simply not forgiving them is illogical and arrogant. Doing something mean to them doesn’t solve the issue, it doesn’t make anything right and it isn’t justice. The only reason I see for such actions are to satisfy one’s pride and anger by punishing them, albeit not physically. It is easier to tell yourself that your friend is to blame and that avoiding them is justified since they to some extent are a bad person who deserves to have something bad done to them in return.
When you allow your negative emotions to control how you treat a person, you disrespect them, the person who previously you considered a friend. No mistake is worthy of such treatment, because if you truly saw this person as a friend you would not hold something as unreflective as a mistake against them. This sudden change in how you see a friend is not logical unless that person has revealed themselves to be someone who you never would have been friends with. This is unlikely in most situations because when you befriend someone you generally see something deeper than just someone who you enjoy being around, there is at the very least a subconscious appreciation of some trait inherent to them, a deeper human characteristic that you see as good. Unless you completely misjudged a person, most likely by them hiding their true beliefs from you, it is more likely that you’re simply using their mistake to judge them. You might also think that their mistake is reflective of who the person really is, but really are just focusing on a specific character flaw and using inductive reasoning to judge that person based on that flaw that you think defines them as a whole. Even if this were true, it does not make them irredeemably bad. To harm or simply throw away your friendship over something that doesn’t reflect your friend’s beliefs is just a reactionary act of angry desperation.
Ignoring or blocking communication with someone doesn’t do anything productive, it just makes you feel better by punishing them and branding them as a criminal to some extent as a means to point blame. By blocking communication you stop any transfer of ideas, and therefore you prevent discussions which are necessary to determine the truth through logical arguments. This is being close minded, which is never a good thing to be. This prevents your friend from trying to explain why they did what they did, or to apologise for it. Even if you block communications after they have said these things, you are not allowing further dialogues and thus not allowing reconciliation.
There is no crime that justifies being mean to someone. When you punish a friend in these ways for a mistake they have made, they are not the ones who have been a bad friend by making a mistake, you are a bad friend for choosing your pride over someone you care about. There is no such thing as unforgiveable acts, it is always possible and justified to forgive someone. Forgiveness is not determined by the person at fault or the graveness of the crime, it is the choice of the one who has been wronged. When someone says that they cannot forgive someone, the only reason I can see for that is that what they mean is they feel so wronged that they cannot forgive the person because that would leave them without someone to blame and be the target for their ire. Without an outlet to sate their anger, they would be forced to deal with the issue which brings pain. Avoiding your friends for a mistake they have made is really just avoiding truth and dealing with reality.
There is no reason to be mean to people, anger and blame will not solve any issues. Solve issues by talking about them and letting go of anger, and realise that people are more important.