In order to permanently disable them, you have to glitch outside of the map in the sky bubble, fly up to each of the towers in turn and place a wall or other object blocking the cannons.
Alternatively, download a map with it done for you here:
http://www.bungie.net/Online/Halo3UserContentDetails.aspx?h3fileid=70824577
You will need a Bungie.net account with a linked gamer tag to download it, other wise you will have to do it yourself with a tutorial from YouTube
You have to set a Trip Mine to keep spawning.Then you keep throwing Trip Mines in a pile till they explode.This will overload the map and the Guardians will not shoot you.
Over load the map with trip mines
Violence is the answer
In halo One Combat Evolved Or any other halo games for pc,options are available to turn off images of blood and gore.
start halo/go to settings/video settings/decals/off
go to options and turn off decals
no
In halo combat evolved you can go to settings and turn decals off and there will be no blood (except blood from the convenant which is blue and purple)
no
no
no
yes you can