This just seems like an extension of what I call "St Trinians Syndrome".
Announce you're having a fancy dress party, and all the women are instantly getting their kit off - 60% will turn up in micro-gym-slips, stockings and suspenders, and 40% will turn up dressed as tarts.
New version: announce you're protesting something, and before you've even explained what it is, half of 'em have already got their kit off.
Men are natural voyeurs and women are natural exhibitionists.
i don't think there is 'the way' to protest - just various ways, of which this is one.
I can see that it will grab media attention - but maybe for the wrong reasons.
An attractive woman bearing her breasts at a camera as a protest against sexism does have something of a mixed message - maybe the placards on their own would be more likely to be read and considered.