What point? That you are a lot more likely to be KOed by smaller gloves? MMA guys don't have weak chins in general. They can take a plenty good pounding. BUT it's a lot easier to set up a KO shot when your opponent has to worry about low kicks, takedowns, knees, elbows, etc... etc... In MMA you can't just shell up and absorb the punches the way you can in boxing.
I mean good lord, Hendo took like 40 knees straight to the face in one of his fights and still won it as I recall.