Upon reading this the next day, I realize it could use a concrete example:
"We should pass a law to strip all legal rights from, and enslave, everyone who is of [pick some minority group]. Neither I, nor most people, belong to that minority, so most of us will benefit from this slave labor."
That's a logical argument. Thankfully, most people today would find it morally repugnant and unacceptable.
Typically it's not that sound arguments shape our moral positions, but that our moral positions determine what we consider sound arguments.