I agree with you that "We have to give people credit for their own God-given intelligence in being able to think for themselves when presented with Catholic teaching".
When my children were quite young and we had discussions about our faith, I remember they understood Godís Love for all humanity but couldnít quite understand why everyone wasnít Catholic. This was an issue as my children attended catholic schools but the majority of their friends at school never practiced their faith and many of the students at the schools were from protestant families. (Catholic schools in Australia?----- thatís a whole other story). I would relay a scenario like the following to my children so they could understand better.
Suppose through lifeís circumstances one of you lives very close to me here but the rest of you are spread across the globe, Siberia, Africa, New Guinea, Indonesia etc. and I wanted you to be safe at home with me. I would have to give you all different directions to get back home, one would have to go west, another east, another south, one may have to cross rivers and another climb mountains but these directions would get each of you home safely. That is what God has done for all his children some are living far from him but he loves them and wants them home safe. Some people arenít given everything like we have in the Catholic faith so they are on different paths to home.
I believe it answered that question at the time but of course there always were other questions. Even now!