"Darwinist" is a word coined to have negative connotations. A Darwinist is presumably a supporter or practitioner of a doctrine called "Darwinism" (which is a companion word coined for the same purpose). It's a subtle thing, and I imagine it works only in English. It's similar to words like: Chauvanist, Leninist, Maoist, Marxist, Mesmerist, Onanist, Papist, and Satanist.
Interesting. I don't find the term to be in the least bit offensive, just hilariously inaccurate. I honestly don't know a whole lot about Darwin as a person; most of what we know about evolution now has little to do with his own personal research, anyway. It's as if antagonists think the modern theory of evolution hasn't moved forward since the man passed away and adhere to his ideas blindly without the benefit of any further research. Quite strange.
Many teenage boys subscribe to onanism whilst they are mesmerized by Victoria's Secret catalogues.
...then they graduate to the Internet.
Cheers!