Should we interfere in other countries affairs?

As I was younger and probably more naive and idealistic, I thought that we shouldn´t intervine and tell others how to live. Now I am still on the same ideals, but I percieve that things aren´t black or white and that it´s a hard task. The West have a certain values and democratic systems. We have come to the conclusion that it´s the best way, because we ourselves have come to that sometimes with blood. I think all countries should decide what type of society they want to have. But…once travelling to Venezuela and seeing the Yanomanis (hidden and isolated tribu in the jungle), I was uspet because there were western doctors. Later I was told, that Yanomanis were gratefull because due to this external “contamination” they had been able to overcome a couple of infections. So where is the line of intervention?. Under the term of traiditions many atrocities have been commited. Should be be quiet and understand lapidation?. Should we understand whale fishing because its part of some countries traditions?. Should be allow clitoris ablation?….I am really doubtful.