Remus didn't like the idea of stunning him, but he truly couldn't think of anything else to do. At least that way they could get him away from ..whatever it was he was doing. He also agreed with James' idea to not let Peter witness any of what they were seeing. It was hard enough as it was; he didn't need to see that.
"You stun him, I'll get him. But where are we taking him?" He asked. Taking a stunned Sirius back into the castle seemed risky. They couldn't fit his rigid body under the cloak, could they? They could avoid people with the map, he supposed, but it was still a risk. They had to act fast, before Sirius was on the move again. "Suppose we could figure that out after you stun him. Do it."