I can see where you are coming from but making an honest light hearted joke about kerb crawling, in my eyes at least, is hardly a hanging offence.
What makes me laugh is prostitution is not illegal, yet picking up a prostitute (or kerb crawling) is, the law is an ass! There are many legitimate reasons people use prostitutes and to avoid offending anyone I shall leave it there.
I also understand where you are coming from in relation to your story of working for the scouts, I had similar jokes made at me when I volunteered at my kids primary school, being the only male in a school full of female teachers and staff. I am strong enough in myself and my beliefs to just brush it aside, hope you did too.