I think parents have to take a lot more accountability for how their children turn out, rather than looking to blame 'famous role models'. How many parents of those same kids will also be sat in the crowd, or watching on TV, and yelling and bawling at the officials and opponents players on a regular basis?
When you see people win awards, they always thank their parents for helping them becoming the person they are, etc. I've never see any thanking Rugby or Tennis players or anything. It may play a tiny part, but the person themselves, and the constant daily influences directly around them (family, friends, etc) are far more responsible - positive or negative - than the behaviour of different sports stars as they compete in competive sport. They might be an easy thing to blame when you're looking for an excuse, but it's really not up to sports stars how people turn out.