Q.Why does he talk about 'mankind'? What about women?

Mill's harm-principle passage uses the older, gender-exclusive word 'mankind', reflecting how 19th-century political writing was commonly phrased even though the principle it states is meant to apply universally. …

Mill wrote On Liberty in nineteenth-century Britain, at a time when formal political and civil rights — voting, holding office, full legal standing — were still largely restricted to men, and it was common, in that era, for political writing to use words like 'mankind' loosely to mean 'humanity' in general, without much thought for how that language actually excluded women from the picture. This is exactly the kind of gap the margin question is asking readers to notice: a principle stated in universal-sounding terms was, in its actual historical context, still expressed through language centred on men. …