I've cancelled my RSPB membership.
I looked at some of the other RSPB "Women Only" walks and one shows that the RSPB do understand why some women need to feel safe. This means they also know they're deliberately compromising women by allowing men on many of their other "Women Only" walks.
"Why Women-Only?
Many women in the UK have sadly experienced harassment at some point in their lives. We know that going out alone into the countryside is something that many women don’t feel safe to do. As a way of supporting women to both feel and be as safe as possible on our nature reserves, we are putting on some events that are exclusively for them. These events won’t be to everyone’s taste, but hope it will allow those, who might not otherwise feel safe, to experience nature in a friendly and safe space, removing some barriers in the process."