If we talk about belief, we cannot avoid the topic of compromising or adhering to what we believe. The claim says compromising is more harmful than insisting. However, from my point,we have to learn to compromise for adhering to belief may birng harm. 
Adhering to one's belief may let a person go extreme. While compromising may prevent this. From this point, it is true that adhering to beliefs may be worse than compromising. If one insisits on his belief, whether it is right or wrong, he may do something that may harm the safety of the society. Terrorists are the typical examples. They believe that their explanation about peace, about race independence is true. Thus, they are willing to do anything under the guiding of their cherished beliefs, even these actions may harm others and even sometimes require them to sacrifice their own lives. We can often read such events that two terrorists killed themselves as the human bombs. Everyone who know the news may wonder: what if they do not adhere their wrong belief? They may enjoy the peaceful life as others. They do not need to kill themselves in a yong age. Therefore, we can see that insisting on his belief may bring negative consequences since a person may go to extreme easily and do something that have bad effects.
Also, we  know that the dream and reality have differences so that we have to adjust our belief and our dreams. Thus, here comes the necessity of compromising: we have to adjust our goals to adapt the reality. For example, for an ambitious running player, he may hold the idea that he can run 10000 meters a day in his training. But considering the reality, his body condition, he has to compromise and adjust his plan of ruuning. He may have to shorten his training distance at first, and then add the distance little by little. From this, we can say that compromising brings no harm but good consequences. Only by seeing the real condition clearly, can we achieve our goals step by step.
However, in some situations, compromising may even more harmful than insisting. Since our belief is something that we have strong faith in, we may live under the instruction of our beliefe. If we give up, we may find our that our life is losing direction. Consider a person who believe that working hard leads to good life. And he always works hard to achieve his dream of goo life. But one day he compromises and he starts to think that working hard brings nothing than tireness. Then he may not devote to his work since he loses the motivation which encouraged him in the past. Thus, losing one's belief can be dangerous, since  people may not behave well when he suddenly compromise and abandon his belief.In all, I do believe that compromising or adhering to one' belief may do harm to a person. As to whether is worse, we have discuss case by case. Also, we cannot deny the importance of compromising in life. In a word, things about beliefs are complicated.