Pejoratives should be avoided, yes.
"Darwinist" is a pejorative. So is "Cretard." Neither is helpful in a rational discussion.
Folks slip up sometimes, but those terms should be avoided in a reasoned debate.
However, now that I think twice upon it,
I HAve lost count of the number of threads that quickly strayed from discussing the info in a posted article, and went to the divisiveness of name calling, of posing and posturing, bringing out other perceived differences or grievance. I've seen 'darwinist' used in context of crude insult, but it is sort-of news to me, that the word itself is offensive. Maybe it is, at least in part, because of the way the word has been used/abused? I could see that, if that goes somewhat towards the 'why', of it being offensive.
Shoot, I'm sort-of doing it right now [discussing issues not narrowly related to the article posted, but sans insult, or even the desire to 'insult'].
Typical FR thread-hijaking I'm indulging in, I guess ;)