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> Every studied history?

A little. Broadly, the things that historical people considered "good" and "bad" are still considered "good" and "bad" today – discounting brief thousand-year fads (which largely boil down to how and whether to signal allegiance with particular ways of organising society).

> Do you eat factory farmed animals?

So you, too, understand that factory-farming animals is wrong – and that many people eat factory-farmed animals despite knowing that it's wrong, because very few people are paragons of moral virtue.

> Currently some leftist group is trying to justify Female Genital Mutilation.

You believe that leftist groups in some sense "should" be more moral than… I'm guessing the comparison is "rightist groups", perhaps the various contemporary fascist governments. But you've correctly pointed out that FGM is wrong, and that identifying with a contemporary political label or ideology does not automatically mean you're in the right.

I fail to understand why you think this is a gotcha. Your comment only functions as a gotcha if we all broadly agree on what's right and what's wrong.