But he doesn’t do that when there is flimsy glass table in front of him.
A person has the habit of throwing whatever is there in his hand when he is angry.
But he may not do that when there is a $1500 brand new phone in his hand.
A person has the habit of kicking something in front of him when he is angry,
But he may not do that when there is thorn bush in front of him.
So if you notice the common-thing here,
When a person is angry— most of the times— he subconsciously knows how to show it without hurting himself.
The extension of this behaviour is,
You show anger only on people whom you think are not stronger than you and who don’t have the power to harm you back.
For example:
When a server is pouring you water and it spills on your shirt, you will shout at him. But, when your boss is passing you coffee and it spills on your shirt, you might not shout. You may even smile ‘It’s okay.’
You will think twice before you show anger on someone who is more powerful than you.
But with people whom you think are lower than you or whom you take for granted, you show it effortlessly. Because you are clearly aware, they can’t hit back at you or that they will come back to you irrespective of whatever you say during anger.
