My answer is focused on the sessions that usually occur within a larger conference.
The purpose of a successful session is to leave the attendees energized and feeling more confident so that they can be more productive. Please be sensitive to the fact that women, for whom those session are focused, have come to a career in science with the lifetime of acquiring not-particularly-helpful baggage from whatever typical cultural biases they negotiated previously.
I have never seen any of these sessions be closed, (there are no bouncers stopping people at the door for lack of bosom) simply that the circulars and announcements strongly emphasize that they are for the women (for the women's benefit). They encourage an atmosphere that will end up with a room full of women scientists (senior/midcareer/junior/student). The attendees, thankfully, tend to self-select for being truly supportive.
Typically, there will be some formal presentation on results of current research on stereotyping and bias, prevalence of impostor syndrome, etc, and its impact on career or motivation and confidence. In a well-run session, the primary purpose of such presentations or panel discussions is not to initiate a spiraling negativity of people comparing terrible experiences or feelings, but to get the information out because these facts are powerful. It helps in confirmation of experiences ("maybe it isn't all in my head after all") - or it simply can be comforting to realize one is not alone ("I'm not the only woman who feels like my successes are probably a mistake"). The sessions that are useful will focus then on making connections, networking, and helping women 'mentor' themselves, showing successful examples.
I have been in a STEM field over 30 years. In my 1st 10 years, I used to be surprised when I saw my reflection off of a window when walking in a street with colleagues. ("Who is that strange-looking person with them? - oh that's me"). Contrast that with having the occasional opportunity to be in a room of scientists, and also majority women. That is a pretty neat in itself, and also is a 'safe' space to ask questions or to make observations and get feedback. It also was very interesting personal observation to recognize a different level of personal comfort being in a space; most of the attendees share similar experiences/feelings that my male colleagues typically have not had (or at least not so pervasively common throughout their career).
I hope that the supportive OP would be self-reflective enough (and informed enough) by now to recognize that we all are 'biased' and that cultural stereotyping and its impact did not disappear overnight. The 'insulted' feeling is natural, (feeling as if you are being told you are inadequate?) but beside the point and not helpful. Perhaps by now you can laugh at yourself a bit realizing that what it sounded like (to me) is that you are so confident about your natural place in STEM that if you feel insulted, you assume it must mean that someone else must be wrong or that it deserves pacifying and explanation. Statistically, women in STEM are a lot less confident. The workshops are to help give little pushes to overcome those insecurities.