Detecting those ports is not conclusive evidence that the person is using a proxy server at all, even less so that it is some annonymous proxy and they are a 'troublemaker'.
And just to repeat - in case you missed it in other threads - millions of people (esp in the uk) have to connect via proxy servers because they have no choice (their company or ISP force them via one).
The scanning I'm referring to is for open (unsecured) proxy ports. This would not affect UK hosts, AOL, or any other host that uses proxies with secured ports.