If you're talking to men, focus on the fact that normal birth is safer for mum (since their primary concern is the wellbeing of their beloved) and back it up with stats (men love numbers).
You can access lots of stats on CS at the Caesarean Awareness Nework website:
www.canaustralia.net
Importantly, they need to know how much higher is the risk of infection, babies in respiratory distress, PND, breastfeeding difficulty, and maternal and newborn death following CS.
You can also look for Department of Health stats for your state on rates of intervention for each hospital: episiotomy, maternal or newborn death rates, length of hospital stay (a good indicator of how able mum is feeling after the birth!), PPH and CS. If they can see that their chosen hospital has higher intervention rates, it might prompt them to ask why.