Answer:
There are many disadvantages of exclusion in societies. One disadvantage is that social exclusion creates parallel sub-societies and sub-cultures within a society, that threaten the social order of a particular area.
Another disadvantage, related with the first, is that exclusion leads to little dialogue among different social groups. This can greatly increased social conflict, political extremism and radicalization, and in extreme cases, as history has shown many times, could lead to civil war.