Shooting them would not be murder or animal cruelty, but I still do believe and always will believe that doing that or catching them and putting them up for sale on CL is wrong. I'm but not trying to preach at you but there are better ways to deal with this problem. Not many people want roosters...
Get a bigger rooster to show 'em who's boss! My rooster can fly out of his fence but the hens can't so if another rooster came he would send him home.
I wouldn't advise catching them and putting them up on Craigslist. They don't belong to you. Put up a fence or talk to your neighbor before you...