Are you actually losing any queries to this site or seeing a drop in your traffic? Google is very smart, they probably know your site is more trustworthy and had the content first. If the person is hosting a bunch of similarly crappy pages on the same IP and/or the same host, Google knows about it.
Any suitably popular site is going to have all sorts of people ripping off your content. Google knows this, and work very hard to deal with it. I just searched for a bunch of things related to your site and the legitimate pages appears to be winning them all, and I don't even see the bad page showing up in the top 10.
If the site is sapping traffic, file a DCMA against their hosting provider (though there are some shady web-hosts who won't do anything about it). Obviously if they are filing a DCMA request against you, defend yourself. But just because somebody is ripping off your content doesn't necessarily mean you need to do anything.
Any suitably popular site is going to have all sorts of people ripping off your content. Google knows this, and work very hard to deal with it. I just searched for a bunch of things related to your site and the legitimate pages appears to be winning them all, and I don't even see the bad page showing up in the top 10.
If the site is sapping traffic, file a DCMA against their hosting provider (though there are some shady web-hosts who won't do anything about it). Obviously if they are filing a DCMA request against you, defend yourself. But just because somebody is ripping off your content doesn't necessarily mean you need to do anything.