Ok I'm late to the party but yeah I think it does actually seem like men are overconfident and more aggressive in conversation than women. For a long time I wasn't sure if it was just selection bias or being primed or something.
Mostly this comes after seeing a lot of men in CH very confidently say things that I think with a lot less confidence, and I'm like ??? I could have just said my thought louder and with less upward inflection and people would have listened to me more??
There is a trade-off between confidence and avoiding conflict. Women tend to pro-actively avoid conflicts and prevent confrontations. Being less assertive is downstream of that goal.