An argument to go with that assertion would make your post more useful.
While it doesn't address your concerns about ethics, recipes are explicitly not covered by US copyright law (obviously there are other factors involved here, but that's certainly the big one).
There may be ethical questions here, but there shouldn't be any legal concerns (IANAL, just a guy in the process of building a site in this space).
Recipes aren't but images always are. Collections of recipes (such as a cookbook) are also protected.
Would it still be unethical if the source was shown when displaying the scraped recipes?