“a better example the Council of Nicaea, who is right. Objective truth tells us both cannot be right.”

Going into Nicaea, the Arians said Christ was fully human, many others said Christ was fully divine, and some held an intermediate position, a mix of human and divine. Objective truth tells us they can’t all be right. The Council asserted Christ is fully human and fully divine, ie they were all right. 
Fully human, as long as you don’t say not divine; fully divine, as long as you don’t say not human. So much for Objective truth saying both cannot be right.