When Treyarch makes trailers, they use god mode to advertise very important and fun pieces of the map. Of course it is almost impossible to get all those zombies together without dying. So, for cinematic purposes they built up the zombies and had him stand there and fire, like, two bullets.
In conclusion, mods are used for filming and glitching is for the malnourished in skill.
If you want to glitch that fine, I don't care but when glitchers dominate the top of the leader board making me have to play games that take 10+ hours just to get in the top 10000 then I start caring. Also if your going to sit in a glitch, chances are you wont be around to help revive me if I get in trouble. (Accidents happen) So if you want to glitch fine. If you want to glitch until you get a leaderboard rank, that's not fine. Play it how you want to don't destroy the leaderboards in the process please.