When someone shares their own ideas and thoughts with us, they are sharing part of themselves. They are going out on a limb, trusting us with part of themselves. If we reply immediately with a contradictory idea, it can really hurt. However, if we treat the ideas and thoughts with respect, interest, and validation, we are in turn showing respect, interest and love toward them. When we hear commonalities with what we think, focus first on those. This builds a basis of understanding upon which you can grow. Then, if the other person wants to hear our feedback, we can share it with them. If we don't know if they want the feedback, we can ask first. Many times they just want validation and encouragement.
Love and respect are more important than giving feedback. When the person wants the feedback, then we can give it without taking away from showing our love and respect for them.