I don’t believe it was just machismo. From Zimmerman’s call to the police it sounds like Trayvon was casing the place. When Trayvon was staring at him and coming forward Z said he had his hand in his waistband and was coming to “check me out”. Seemed like he was afraid that Trayvon might be coming at him with a gun and with an attitude, saying something like “I don’t know what’s his problem.” He asked how long it would take for the cops to get there and said the punks get away so often. The dispatcher said to let them know if Trayvon did anything else. Then as Z was describing the exact location to the dispatcher, Trayvon started running away - headed toward the other exit to the community, Z said. Z followed for about 28 seconds, stopping after the dispatcher said he didn’t need to do that.
So anyway, he wasn’t defending his family from ferals but he did seem to think that the guy was casing the neighborhood. Knew Trayvon was staring at him and then coming to Z to “check me out”. Knew Trayvon first had his hand in his waistband and then had something in his hand so Z might well have suspected a gun or other weapon. Was concerned about giving out his home address because he didn’t know what Trayvon might do - which suggests he thought that Trayvon might have a gun.
IMHO, it also suggests that Z. was thinking of Trayvon having his home address and maybe making a visit to Z.’s house.
That would indicate that Z. wasn't thinking ahead of time of shooting Trayvon. Hard for a dead fella to come to your house to cause trouble in the future.