Defending is the word, and it is a defense.
When you admit something awful was said or done, and then say oh but these were wonderful parents, there is a gap.
The most wonderful parents aren't perfect and don't meet all needs. And some wonderful parents are more wonderful to those outside the family than to those within the family.

Defending our parents is something learned when we are young, when we are powerless and don't have any other perspective. It's a survival tool, and self-protective.

I don't think your therapist is disapproving of your doing this. I am sure she understands, yet she also wants you to be able to look at these things without that defense. To just look at how it affected you, your feelings about it that are the starting point of your defending.

"I feel crushed when my boss criticizes me harshly in front of others" is true and it is about how someone might really feel in that situation. That true response and feeling can be minimized and even denied by immediately jumping to "But he is a really good boss!". He may be a really good boss... AND... I feel crushed when he criticizes me harshly in front of others.
Both are true.