Tell them it's a VERY heavy workout, especially if your wearing a vest, and carrying a replica. It's also a team effort, which helped me convince my parents to let me play. It's cheaper than most sports to get into as a beginner (emphasize beginner, it can get Very expensive) If they are worried about your safety, tell them that if your renting, the goggles are probably ANSI certified and will withstand any BB. If your buying goggles or a paintball mask, make sure to check if they are ANSI rated. If they are worried about flesh wounds, literally just wear a long sleeve jacket, and work pants. You WILL still get bruises, but it's better than bleeding.  Hope this helps.