Starscream is rather used to others attempting to use their side to push him around, as long as he doesn't have a fusion cannon placed right up against his head, he's fine. Which is why he gives Megatron a look, but there is no cowering or any other movement.

"That depends on how much you'd care if the other me happens to disappear in some sort of sudden and tragic 'accident.'"

Starscream himself didn't like the idea of another 'him,' he had enough with that stupid clone. Then again, isn't the Earth saying 'two heads are better than one' ? Maybe. He'll have to see.