Unless you are very overweight and/or badly out of shape to begin with. Then it is actually possible to build muscle while in a deficit.
And, even more, it's also possible to build some muscle in a calorie deficit *if* you are eating sufficient amounts of protein.
Regardless, you can *maintain* existing muscle while eating in a calorie deficit by adding weight lifting and / or body resistance work to your efforts while dieting. That way you insure that you lose maximum fat and minimum lean muscle.
This is where we differ. I think your wrong, you think I'm wrong. Now should I call you a troll and be done with it?