As a chicken-raising first-timer, I'm with Cass (*waves to Cass*) in appreciating realistic "this is how to handle problems" threads. I do love my birds and have indulged in some shameless "lookit the cute chickie look look look!" cooing, but I started keeping chickens iin large part as a food source, and do ultimately see them as livestock. Charming livestock, yes, but livestock nevertheless.
We currently have five cockerels who are all about 3 1/2 months old. A couple of them are slated for the stockpot - I plan to process them at 20 weeks or so unless they start acting up and need to be culled earlier for everyone's sanity. The birds headed to Camp Whirlpool are neither crowing nor battling it out yet, so for the moment they get to grow out a bit more. Two of the lucky designated survivors have been selected for their good behavior thus far towards the pullets and towards us. The third appears to be so far down in the ranks that I doubt he'll be a problem for a while yet if ever, and he's too scrawny to bother processing at the moment anyway. If any of them get it into their tiny brains to become human-aggressive, however, they'll quickly be knocked down a few pegs.
I haven't been challenged yet, but I'm sure it's coming at some point. DH was challenged about two weeks ago by one of our frou-frou White Crested Black Polish, but he took care of that problem by grabbing the offender and holding him on his back until the bird gave up. Depending on the level of intensity, aggression towards any human will be met with anything from stalking (which I already do to good effect - all of them run from me if they see me heading towards them) to a boot across the run to an immediate date with the hedge clippers or knife. Unwarranted aggression towards the females will also result in a dead roo walking. I don't back down from the gangbangers and belligerent crackheads who make up much of my pharmacy's patient population - I'm certainly not about to let some eight-pound bird lord it over me.