What is a slut? How do we define that word? I think the connotation is generally meant to be an insult toward a person who engages in sexual promiscuity, with an implication not of mere sexual license, but some form of indiscriminate or otherwise reprehensible behavior. By that token, 'sluts' may deserve some amount of condemnation, because they are engaging in risky and poorly thought-out activities. But all too often, the term 'slut' is used to indiscriminately criticize sexual expression and activity that is, in truth, laudable from a humanitarian but not sex-negative perspective.
You see, the real problem with slut-shaming isn't that sluts (by our definition above) are being shamed for engaging in slutty behavior. The problem is that normal girls are being dissuaded from expressing their sexuality at all. The solution, then, isn't necessarily to praise actual sluts or slutty behavior, but to find that middle ground that allows - even celebrates - sexual expression in direct opposition to prudish values, without presuming that all sexual expression is 'slutty' in nature.
Assuming our definition above, conceding that all sexual expression is slutty (with the conviction that that's a good thing) is still submitting to the prude's conception of sexuality. It's like protesting religion by professing to worship the devil. You're announcing your opposition to God, but you're still buying into the religious worldview, and reinforcing the devout's belief that you are evil. If you don't really believe in the devil (any more than you believe in God) because you think the whole system is screwed up, you ought to say as much.
We must, therefore, be able to understand that wearing a miniskirt in public, or speaking frankly about sex, or any number of sex positive behaviors are not the same as sleeping around indiscriminately, or whatever sort of sexual behaviors we might still define as 'slutty' in the sense considered above. Thus they ought not to be criticized, and the term 'slut' should be reserved for someone who makes bad decisions about sex (from a sex positive perspective), and not just anyone who embraces sex from a positive perspective.
In other words, 'slutty' is not a synonym for 'sexy'.
