Yes it is. It's this attitude that destroys multiplayer.
Let me make this absolutely clear : Almost all of the glitches in Gears of War require some level of latency to perform. Therefore, the host CAN'T DO THEM. If the host can't do it, no one else should be able to either, and when they do, it's cheating.
The Live! staff is finally starting to ban people who glitch in ranked games. And I say finally, because ranked has been a joke for months. The game relies on teamwork, yet not only is there no party system, but it's almost impossible to get into your friends games. If you do play ranked, chances are someone in there will be glitching, and the host can't kick them.
There is a small subset of glitches that ONLY the host can perform, such as chainsawing yourself and the unlimited sniper shot, but neither of these do anything besides get the host killed (You don't have to reload the snipe... but it doesn't do any damage either.) The gameplay killing glitches (Super jump, the roadie run where you can still fire, the instant chainsaw, and the slide) can never be performed by the host. The escape glitches can be done by anyone, and they are the worst. You can't kill the person unless you go out after them.