I think this probably is a real issue for many sports and hope staff has appropriate training to identify those who are truly threats and not go on a witch hunt.
In this instance it is his actions that are suspicious, and if other dads behave in an odd manner or display poor judgement I hope they are viewed suspiciously too. My husband takes my daughter to local competitions and I assure you nobody would look twice at him because of his behavior. Similarly our team has a photographer (parent volunteer) who is male and is present for teams that are not his daughter's and he is not given a second look. And honestly, are there really that many dads (or moms for that matter) that go watch comps or pretty much any youth related sport without a personal or professional reason to do so but instead are trying to meet the athletes?