Why did the Western NATO allies side against Christian serbs?

Would it be okay if the Native Americans decided to start a war against and kill everyone that has European ancestors because Europeans invaded and took over North America hundreds of years ago? Would it be okay if the other countries just sat back and let the Native Americans slaughter every single non-Native American? No it would not be okay, just like it was not okay for the Serbs to murder over 300,000 Bosnians and 100,000 Albanians. Was NATO just supposed to ignore the situation and let the Serbian wipe out every single non-Serbian that existed? You need to stop looking that things at an ignorance point of view.