How do you win

When other people's parenting/non-parenting style infiltrate your efforts to raise your child/children in the best way possible how do you succeed.

I received this invitation with a child wearing a costume of a night and holding a sword. How do I discourage my violence intrigued, bad-guy curious, action packed 3 year-old boy not to be interested in such things when some parents are so careless with what they allow their children to partake of. Really now, is the sword necessary and not just a plastic sword a sword complete with what looks like a spiky brass knuckle handle for an extra something in the ass-wompin'. All I can say is I am glad we missed that birthday party.

What are people thinking? Really????