Hatred is hated as the holy Tana says about it that it takes a person out of this world and it drags after itself many other sins and through it he comes to quarrels and saying bad things about people, and it causes him to rejoice about bad things happening and to be a damager, a causer of pain, someone who takes revenge and bears a grudge. he will be all of these things amongst many other evils.
Hatred is a very severe sin as amongst all of the sins there is no other sin which one can transgress constantly like hatred as with every second that he hates someone else, he transgresses that which it says in the Torah “You shall not hate your brother in your heart!”, and also that which it says “And you shall love your acquaintance like yourself!”. It is for this reason that because of the sin of baseless hatred the second temple was destroyed. Every type of hatred is called baseless hatred as all of the reasons that a person gives it order to cause him to hate are all empty, the actions of an illogical mind.
A great evil is hatred which is guarded in the heart of a person when outwardly he behaves towards him as if he was his close friend. This is a great evil without a cure as when the hatred is open and public in the end advocates of peace will stand up and make peace between them, but when it is hidden in the heart their anger will be kept forever and no person will be able to save himself from a friend who hates him. It is for this reason that the Torah commanded us “Do not hate your friend in your heart!”. It is better for a person to choose the lesser of any two evils and if his friend has done bad to him or has committed sins in a way that it is permitted to hate him because of his terrible ways, he should at least hate him publicly. However, the badness of people is so strong that most times when one person hates his friend they do so because of jealousy, as it appears to him that his friend has undercut his business etc., and he is therefore embarrassed and scared to show that he hates him because of this, as he is embarrassed to say that he does not have enough belief in Hashem and is called one of the “small believers” and this type of hatred will arouse other factors until in the end he has accumulated many imaginary reasons for the hatred, whereas in truth all of them can be blown away by the wind as has been explained above.