What about feeling threatened? Does that require defense? What if my brother was scared out of his mind because this is the first time happening to him? So, yes, I was going to fucking attack the person with an illegal fucking weapon. Who the fuck knows what he's hiding in his bike or pockets. He was so close to me that he could of sniffed my ass. It was like he wanted to shank me, do I wait until he stabs me before I can touch him in self defense?
Self-defence law does not care about your feelings, only about actual and threatened assaults (and an insult is not a threat). Neither does the law allow you to attack someone because you don't know what he's hiding, or because he's standing close to you, or because "it was like he wanted to shank you". He has to actually pull out the knife or threaten to stab you before you can use force to defend yourself.
Besides, forget about the law for a moment, and consider the facts. Suppose he actually does have a knife and he really does want to stab you, your attack
gives him a perfectly legal excuse to do so. He will stab you, and in court he'll deny that he ever provoked you (you can't prove he did, remember), he'll say he was only carrying the knife because he uses it at his job, and then claim self-defence because you attacked him first (which you did). Assuming you survive, you're the one who'll be going to jail.