Everyone has a right to their own opinion, and all opinions are equally valuable, aren't they?
It's my opinion that opinions are not inherently equal. If your opinion is stupid or nonsensical, then it is a worthless opinion and no-one is obligated to respect it.
Indeed, but whether or not an opinion is such is a lot of the time relative. Let me know if the following makes any sense.
I find that in a discussion or decision making the parties attempt to overcome and win the "opponent", to gain social an/or other advantages. This may happen at all levels from conversation between two people to parliaments. This is natural, and thus conversations aiming to find the truth or best interpretation of a phenomenon or event is rare. We're still just monkeys yelling at each other and beating chest to rise oneself, offspring, relative or friend to better position within a society. Purpose of a debate, discussion or decision making thus rarely is in finding truth or best course of action for everyone but advantages to individuals or groups they represent, at best compromises and common ground. People are competitive and individualistic, decision making in a society(between entities that have the power to do so) is always more or less dishonest. Dishonest is born out of need of competition between individuals and factions. Fancy words like human rights or freedom or whatever can become just tools in an attempt to gain advantage, real or perceived, way or another to oneself or a group of people while not necessarily adding any value to the entire society.
This phenomenon of inter-society competition at multiple levels and the associated inheritent dishonesty in discussion and debate I believe is one of the reasons why certain organization are very hierarchic, that is, to prevent internal struggles and make decision making as rapid as possible. Societies themselves have structures of hierarchy, but not quite as strong as say, militaries. Common rules(laws), hierarchy and enforcement of those become advantages to a society and every individual within in.
What does this have to do with moral relativism? Well... I think that most morals are just constructs of natural or artificial social hierarchies, rules and customs. We believe that each of our moral is ultimately valuable to us personally, and our society, and they may involve appreciating or not appreciating values differing from our own. A Chinese or North Korean may be perfectly okay in not getting to decide where he or she even lives and thinks its for the greater good of everyone that the entire nation is almost in an Orwellian state of top-to-bottom control. A North Korean's morals and values likely differ vastly from ours, but on personal level at least, the morals have been formed by very similar phenomena.
Sure there could always true, objective best courses of actions to be taken at all times, but humans dont work that way. The man kind isn't a Klackonian hive mind composed of psychic, altruistic individuals.