I know it feels frustrating. Yes, they are lowlife bastards. If you launch an all out fight against them to get it taken down, you might win. You'll also leave that fight angry and bruised. Instead, you could spend that time doing something enjoyable, productive, and ultimately more valuable for the long-term success of your site.
And anyway, your website:
- is on a domain with more trust.
- published that article first.
- is coded better for SEO than theirs.
- is better designed than theirs.
- isn't at risk for serious penalization from search engines.
...so you really don't have anything to worry about.