One of the foremost things that differentiates one human from the next is his culture. Culture is the sum total of all the traits of behaviour that affiliates a person to a certain group of family, which is either learnt or is passed down through the generations. It is a perspective that differentiates them from all the others around them.
What might be right in one culture might actually be considered as a taboo in the other. For instance, while in United Kingdom and US, the thumbs up sign means great, in cultures like that of the Greeks and the Sardinians, it is equivalent to showing one's middle finger.