Because as you have correctly characterized them - ethics are opinions. But ethics are more engrained in the genetic fabric than what would otherwise be described as simple opinions. They're opinions that some people are willing to die for. Worse yet, everyone has one. Don't mak'em right. They're on the order of individual or group belief systems, morals, religions. Al-Qaeda commits suicide bombings to enforce their ethics and morals.
But primarily and most importantly, the guy that created and controls this Forum says so. You don't like it - you know what the alternative is...