Oh I agree, there's no doubt they're both mainly riding a populist backlash against immigration, especially Muslim immigration. I think the parties themselves differ considerably more than the broader wave they're riding, which has more common origins.
DF really do seem to be critical towards "ethnic Danish" subcultures they view as deviant as well, especially in the past year. There's currently a bit of hand-wringing over biker clubhouses (residents don't like having one nearby), and they've been getting out in front of that populist backlash too, which plays well among their base for different but related reasons. It's sort of Public Enemy #2 in things that are ruining Denmark, from their perspective.
Here's a recent story (via Google Translate, note that "rocker castle" means "biker clubhouse"): http://translate.google.com/translate?sl=auto&tl=en&js=n&pre...
