Whatever happens to you was being prepared for you from everlasting, and the mesh of causes was ever spinning from eternity both your own existence and the incidence of this particular happening.
If others go wrong (morally speaking or otherwise) either tolerate or teach. If you venture to teach, do so kindly and use reason and logic. Also, be willing to listen and learn yourself. It is entirely possible that you may be in the wrong.
Next, Marcus reminds himself and us, that whatever happens to us know is due to a complex weave of causes and effects, including his and our existence. Regardless, whatever happens now, we must accept. It is uniquely our fate and destiny and we must do our best to love it (amor fati).
(see also Citadel p. 140, 162, 221, 225-226)