I try not to hurt other's people's feelings, unless it is something that is objective and something which they can learn from.
There are a few factors, I've noticed in people, I try to avoid before considering hurting other's feelings, due to fairness.
1) Justifying current position, people do this as an immature ego defense mechanism. They will look at all angles not necessarily consciously until they can find a flaw in other's actions, to make themselves feel better.
2) Criticising others can be a reflection of the self at times. It is healthy when you are productively self critical, but you might be criticising others excessively due to self loathing.
3) To improve social standing, often people will see characteristics that are just different or normal, but due wanting to be externally accepted and status, they point out flaws, to earn respect.
4) There is a likelihood of projection.
5) Often used to show superiority over the person, or power over them, due to insecurity.
6) Not enough thoroughness in critiquing, can result in incorrect assumptions of flaws, due to lack of data collection.
So in a nutshell, I try to do constructive critcism or very precise critique, to my capacity, if I have to hurt other's feelings. Even if these reasons are presentable and I'm on the other side, it is efficient to see the validity in the comments, taking the proportionate validity in relation to these factors, with a disposition towards learning/personal growth.