One reason why the people of earth are so diverse is because of opinions. Everybody has their own, and lots of conflicts have arisen because of opposing opinions.
I believe there are at least 3 different kinds of opinions: observational opinions, literature-based opinions, and invalid opinions with no basis of fact or observation.
Observational opinions: An observational opinion almost always contains an adjective, and are not usually written in factual literature. For instance, if I were to say "kittens are cute" and "bats are ugly", those are opinions based on the appearance of those animals. While I may hold those opinions, I don't judge animals based on their outward appearance, so my feelings toward cats and bats are about the same.
Literature-based opinions: These are opinions based on written fact or from other trusted literature and people. They don't necessarily contain adjectives. Religious beliefs easily fit this category. In addition, if I were to say "prairie dogs should be saved because they lost 99% of their habitat," that would be considered an opinion based on literature. "Prairie dogs should be saved" is my opinion, and "because they lost 99% of their habitat" is from factual literature that my opinion is based on.
Invalid opinions: Any opinion based on hate, fear, or ignorance would fall in this category. Such opinions usually have no observational or literary basis. The people who have these opinions are close-minded and do not listen to people who hold an opposing opinion. For example, if someone were to say "I hate rodents", it is most likely based on fear of rodents and ignorance of rodent facts. Such people are ignorant of the fact that it is the largest and most diverse group of mammals, and only very few types of rodents can be considered "dirty." See my rodent page.