Many religious traditions have beliefs about vegetarianism. They teach that killing animals for food is wrong. Others see carnivorous behaviour as a natural part of life and eat meat cheerfully. However, there is also a large group of people who believe that eating meat is wrong, and yet continue to do so anyway. Similarly, there are people who may be against sweatshop labour but continue to buy clothing produced under these conditions, and so forth.
It is up to each of us to decide our stance on vegetarianism, sweatshop labour, and the like. Each issues has its set of pros and cons. However, once we have made our decision, it is very important to follow through with our beliefs. Otherwise we lose our integrity.
In addition, we must be ready to change our actions and beliefs should our original premises prove false. For example, we may buy fair-trade coffee, believing this to be beneficial to Third World countries. Then a new study may show that it is somehow harmful to their economy. If this were the case, we would have to change our beliefs. There is no point in stubbornly clinging to a belief if it is proven invalid.
In short, our beliefs have little meaning if we do not act upon them. Furthermore, they will soon become flawed if we are not courageous enough to change them when new evidence comes to light.