Remus had followed right on James' heels, coming to stand at Sirius' right and just in front of him where he'd be able to block any further attempts by fist or wand. He kept his arms at his side, ready but non-threatening with his wand still holstered, and let the wolf rise a bit in his eyes.
"Ron, this is neither the time nor the place for this," he said with deceptive calm, casting a pointed look around at all the happy Weasleys celebrating the life of the young man whose actions were in question, particularly the clan matriarch whom Remus knew with certainly would take the angry redhead to task for trying to start a brawl at her party.