Women Speakers: Has Lowering One’s Gaze Been Limited to Bra Ads?

There seems to be something of a fashion nowadays for sisters to give talks in front of men at Islamic events (without barrier). is this permissible in light of shariah? many of these female speakers are young, and not ugly (speaking honestly). that aside, it doesn't 'feel' right - isn't this going against modesty, which rasoolallah (SAW) said was the sign of our deen? whatever happened to lowering the gaze, or does that only applies to wonder bra adverts now?  

Walaikum assalam wa rahmatullah,

Note that women speaking on stage does not mean that you are now somehow allowed to look with desire.

Given this, the obligation of lowering one’s gaze does not apply only to bra ads: it applies any time you fear that your looking is with desire (i.e. inclination of the heart in a physical way). [Nabulsi, Sharh al-Tariqa]

Wassalam,

Faraz Rabbani