I went over to the Great Chasm and tried this out on a Metang in a double battle with a Haxorus with mold breaker leading and an intimidate Stoutland. The Metang's attack was not lowered. Although Mold Breaker normally effects Clear Body, it seems to only work in regards to the pokemon with Mold Breaker; when my Stoutland tried to use leer, Metang's stats remained uneffected