If they are wise, do not quarrel with them; if they are fools, ignore them. - Epictetus

Furthermore the true Cynic must know that he is sent as a Messenger from God to men, to show unto them that as touching good and evil they are in error; looking for these where they are not to be found, nor ever bethinking themselves where they are.

[8] Yet if we place the good in right choice, the preservation of our relationships itself becomes a good. And besides, he who gives up certain external things achieves the good through that. [9] ‘My father’s depriving me of money.’ But he isn’t causing you any harm. ‘My brother is going to get the greater share of the land.’ Let him have as much as he wishes. He won’t be getting any of your decency, will he, or of your loyalty, or of your brotherly love? [10] For who can disinherit you of possessions such as those? Not even Zeus; nor would he wish to, but rather he has placed all of that in my own power, even as he had it himself, free from hindrance, compulsion, and restraint.

It is the act of an ill-instructed man to blame others for his own bad condition; it is the act of one who has begun to be instructed, to lay the blame on himself; and of one whose instruction is completed, neither to blame another, nor himself.