People who accuse others of trying to be know-it-alls are wasting energy concealing their own ignorance when they should instead be working to further educate themselves.
As such, most of the arguments I get into online these days reveal only that my interlocutor does not fully comprehend the subject (and, naturally, assumes I'm the problem, not her lack of experience or information).
Arguing about whether or not there is always equality of opportunity is like arguing whether or not there was a Holocaust--one side is right and the other is just plain wrong.
And speaking of the Holocaust, those born after it occurred or were not actually involved might not be directly culpable, but we are all responsible. Responsible to remember that this was not only a German atrocity; it was also human one, and we must be ever-vigilant because we're all, each and every one of us, capable of it.
Be ever wary of those who argue in favor of "freedom of choice" when the chooser is not fully emmancipated economically, socially, and/or politically.