It is a gesture of dominance that most men will accept and even enjoy, the same way as a dog accepts and enjoys being patted on the head. It's not an aggressive act, but it is dominant. This is quite clear from the way men respond to it, which is almost universally the same: by relaxing. (Hence you describe it as relieving tension.) However try it with someone who thinks they are more important than you, and it will cause hostility.
There are other universal dominance signals. For instance, keeping eye contact without smiling. Or, interrupting someone who is speaking. Or, being late for a meeting. Or, laughing at someone who makes a mistake.