I have coached kids.. the best advice I can give is to stay out of it, even if it's the most clear-cut thing you've ever seen. It's rare to find a parent that wouldn't be defensive when you're someone they don't really know calling their parenting into question.. They'll hold it against you all season. And the child may even get worse.
Ruling with an iron fist is not the answer, nor is ignoring the behavior completely. If you rule with an iron fist with this one child, you will be expected to do so with the rest of them, and kids will be kids. It's a slippery slope to start kicking kids off the team for kids just being kids. By ignoring the situation, you set a bad example that the kid can do whatever they like without consequence. Kids will do what they are allowed to get away with. Pretty soon, the kids will all be chasing butterflies and kicking dirt at each other. I've been coaching at the secondary level for 15 years now. You can never keep everyone happy, but you can ask parents to be involved in their childrens discipline. If the parent say's "you're the coach", then you deal with it as you see fit. If it means removing the child from the team, so be it, but you have asked the parent to help out and you need to do what is best for the team.
The problem is not with the kid's whining, you are obviously not using him correctly. Play him consistent playing time at his natural position. Oh, and airing your grievances with him in this public forum instead of behind closed doors shows a tremendous lack of class. At this point, I would say you have soured the relationship beyond repair. I'm afraid your only option now is to trade him to another team that can either deal with him or send him back to Greece.
Bingo. Excellent advice. Our soccer youth league has explicit rules prohibiting parental intrusion into the games. In addition, the coach added his own rules. Edit: although, re-reading your title, makes me wonder whether your own attitude may be an additional issue here too. Whiny brat? Weeny dad? I hope you can conceal your obvious disdain for these folks from the other kids and parents.
I think you are doing the right thing. You are the coach for the whole team and you need to make sure that this kid is not disrupting all the other boys. Tell his father that you are no only responsible for his own son, but all the boys there. Is this the only post in the history of this bbs that DD did not add a DD at the end of his post?