I"m so sorry this is happening. Consider yourself lucky he pooped in a "cleanable" spot...not peeing on carpet! I think time is the only answer. Whenever you introduce a new kitty to a clan, someones whiskers will get bend out of shape. If Sam needs to establish his Alpha cat status, the rest will fall into place eventually. Sorry this is stressing you out but it's part of meowmiedome. Try some Feliway (sp?) and let them sort it out on their own. Some extra lovin for Sam might make him less angry at you.