1. Where were you when X happened
2. In the past you did X or Y and hence have been labeled Z. How dare you bring that up now
3. Political group A or B used to do something similar while you looked on, how come you are now complaining
4. Your criticism stems from the fact that you HATE us, so it can not be taken seriously
5. Mr. A or Mrs. B who are universally acknowledged as scumbags are voicing a similar sounding criticism, hence your perspective on the matter has to be wrong.
All to these patterned responses would either put on the defensive or steer the discussion away from the issue that you are raising. Hence, shouting matches ensue, angry words are exchanged, frustration peaks and …. the issue remains unresolved.
If you are lucky enough to manage to neutralize all of above points while maintaining a modicum of civility, the final line of defense is:
6. In this or that country they are also having a similar messy situation, why do you expect that we should be any better?
At this point my advice would be to just walk away from the discussion. Continuing at the point is likely to cause an artery to burst.