A man is very gentle to others, why is he sometimes angry with me?

If you two are a couple,

Because he is closest to you and has many contacts, people have a temper and it is normal to be angry. In front of you, if he has no right to be angry, then you are equal to ordinary friends.

If it is an ordinary friend.

Being angry with you all the time means that there is something wrong with treating you as one of our own, and there will be thorns in your words, so you won't hide anything from me.