I do not agree with you about the views relating to those born in Theravada countries (I do not have the direct knowledge if Sri Lanka so I will not generalise any statements that far)I just want to respond to this question in a different way. It is too easy to defend the religion of your choice. Eg . if a person is born in Thailand, it is easy to defend Theravada or if my teacher is a Tibetan Buddhist nun, so I defend Vajrayana.
Simply, because of your culture and background.
Similarly, a person born in Taiwan would usually defend Mahayana.
Much more difficult to approach the debate with an open mind. To look at the different schools as a scientist would before coming to any conclusion.
First of all, you need to look at the history. Then you need to look at how it is practiced today.
And always remember that the most popular forms may not be the most accurate representative of the school.
But what usually happen is people just defend the school they like and criticise the other schools without knowing much about them.
My view is that I was born where I was because of my karma - that is why I was exposed to Theravada Buddhism from birth. I hold the view that some born somewhere else with any of the other forms of Buddhism are likely to follow that form. All of us have hurdles that we have to overcome - just as our karma is different so are the hurdles that each individual has to overcome is different. I think that the important thing is that everyone follows the path the best resonates with them - even if that is a completely different belief system. If someone ends up following a Theravada path after following a Mahayana path they owe that path the same respect as they should hold their parents in - because it has brought them to this point. The same should also apply the other way.
What I have seen in my travels people being more susceptible to defensive posture is where they have converted and for some reason feel the need to defend their choice; or where people live at the geographical junction of religious beliefs. Your following post illustrates that point very well I think.
metta
dagon