We're getting into the offensive territory here so I must be careful to what I say.

Let's take the example fo Aristotle, who declared that slavery was a natural state to some people. This may seem offensive, but it spawned from the observation that some people aren't capable of taking care of themselves and must rely on somebody else. In the past, these people were slaves. Today, they receive social security checks. The truthfulness of the principle on which Aristotle's statement was based is positive, but due to the fact that the statement contradicts the principle of egalitarianism established after WWII, we're not allowed to voice the observation, or simply accept that Aristotle was indeed correct.