Based on the additional information provided in the comments and to paraphrase the question: You are concerned that an unknown male parent in a public park and with their own child of a similar age might abduct/harm your child from right under your nose while you are watching them play a game that has no inappropriate content whatsoever. All this while presumably there are also other children and parents around.
It is natural to be concerned about the welfare of your child there is a point at which such concerns and worries leave the bounds of rational behaviour and decision making.
From the way you've described the situation and your reaction in comments I have good reason to believe that this may be the case and it is something that you need to seek support, possibly from a professional about learning how to manage. If you don't then there is a genuine consequence that your child will become so risk averse that their ability to get on in later life will be severely affected.
Evidence shows that the majority of the kind of attacks on children you're most concerned about come from people well known to the victim and their family (Nearly 72% according to one study of cases in 2006/7) - precisely the people you've known for years who you feel you can trust. Such incidents take place quietly and behind closed doors.
Life is about risk and reward; you need to start working out better ways to weigh up the two. Right now you're so wrapped up in your little princess that you think you can protect her from everything, and that's being a caring parent. There comes a time when being a 'caring parent' means that you will cause long-term developmental issues for your daughter.
Unless there is a specific risk backed up with evidence then you have overreacted massively by trying to teach your child to avoid other children's parents. In the case of a "known" risk (even if you do not know their identity) then steps to mitigate/reduce that are often very different anyway.