A few years ago a request went out from our local guild for help with a ringers' tea at a ringing meeting. The request was very specifically only sent to the female ringers at our tower. I replied and objected to this, saying that men can make tea and sandwiches too. The cheerful reply I got back (from the female guild secretary who had sent the original request) was that her husband wasn't good at such things. She may then have gone on to ask all the ringers for volunteers, but the assumption that women would make the tea made me specifically not volunteer to help, and my husband helped instead.
If we see specific examples of bias in whichever direction, we need to challenge them otherwise people will never see the effect it is having. Equally, if someone feels unable to challenge bias they suffer from, others need to stand up for them too and point out what is happening.