I was tempted to give Siam as a successful example instead, if only because they managed to never be colonized,
The reason Siam was never colonized was that it served as a buffer state between British Burma and French Indo-China. This suggests another method to avoid colonization. Play rival would-be colonizers against each other.
In order to have a useful conversation about the topic it will be necessary to challenge his implicit claim. If he insists on making that impossible then its not possible to have a reasonable conversation with him.