Credible to whom, exactly? Clearly the person under threat of assault, being violently confronted by the assailant thought so.
You don't need to wait until someone draws a weapon, which you may or may not know they have, or wait until actual physical violence is being done to you before you multiply your force, and put an end to the threat.
Bottom line, don't engage in violent anti-social behavior if you don't want reasonable people to shoot you.
No one is under obligation to endure a beating simply because you want them to.