Learn to deal with bitter people

Some people starts off innocent, friendly and kind to others.
As time goes by they start to encounter horrible people with rude manners (due to mental afflictions cause by distressful environment etc...)
So these friendly kind hearted people become defensive and shock
and eventually may even become bitter, cold, stern or even mean to others.
However, the person can learn to escape from this negative response and handle it postively.
Being bitter and mean isn't the only way to deal with being abuse.
One should learn to recognize and be mindful of rude, mean trouble makers
Learn to ignore them and stay away from them
Learn to be patient
Learn to let go of the afflictions and ill will against them
Basically learn to be immune to them and not waste time of them unless it is for the best spiritual benefits.

Just how we learn that certain things can be not wholesome like out of date milk,
We don't need to hate it and be bitter to it like an immature person
wasting our energy, time, emotion and life on such thing.
Just know it, ignore it, avoid it, let it go and be at peace.
Take negative experiences as a way to grow more mature and sensible, to handle things appropiately. That is wisdom.

Do not trade your calmness, peace, dignity, kindness and virtue (light)
for anger, bitterness and revenge (dark).
Grow positively through these experience with mindfulness, patience, forgiveness, letting go and tranquility through these experiences.
Handle the situation positively, growing your virtue and wisdom.