Explaining it all is where it gets complicated. Unisex clothing was a reaction to most of the gender binaries in fashion: long hair/short hair, skirts/pants and yes, pink/blue. But what alternative was posed, and why? For the most part, unisex meant more masculine clothing for girls and women. Attempts to feminize men's appearance turned out to be short-lived fads, not permanent changes. The underlying argument in favor of rejecting gender binaries turns out to have been another binary: a forced decision between gender identities being a product of nature or nurture. For a while, the "nurture" side was winning. Gender roles were social constructed, learned patterns of behavior and therefore subject to review and revision. Unisex fashions were one front in the culture wars of the late 60s and 70s -- a war between people who believed that biology is destiny and those who believed that human agency can override our DNA.
Thanks for listening/reading to my ponderings. Comments most welcome!