All you need to do is look at the horrors of various "Ethnic/Communal Cleansing/Riots" etc. in various countries across the world. Eg. 1) Ethnic cleansing during breakup of Yugoslavia 2) Communal Riots in some of the countries of South Asia etc. In many cases it was literally neighbour-vs-neighbour all because the environment changed to expose and sanction to act on various fault lines eg. ethnic/linguistic/religious etc.
All you need to do is look at the horrors of various "Ethnic/Communal Cleansing/Riots" etc. in various countries across the world. Eg. 1) Ethnic cleansing during breakup of Yugoslavia 2) Communal Riots in some of the countries of South Asia etc. In many cases it was literally neighbour-vs-neighbour all because the environment changed to expose and sanction to act on various fault lines eg. ethnic/linguistic/religious etc.