Peleus knew that confrontation was near, Achilles had a lot of anger that he needed to let out, but Peleus would not be just another villain for him to take down. When he turned he put a hand on Achilles' shoulder.
"Achilles," was all he could say hoping it stilled the warrior. He owed Peleus respect as an elder, as his father. Wasn't the golden warrior not reacting as childish as his own son had to him. And yet it seemed justified here if only because Thetis was involved.