I wasn't making a legal or moral judgement, but a practical one: applications designed for downloading copyrighted content disproportionately tend to contain malware.
Nonsense. For every legitimate example of such a malware-infected program you can think of or find, the community can point you to at least X others that are completely clean.
Your suggestion is not a practical one, but rather an opinionated one.
Maybe it's because I'm on linux, but torrented content never gave me any viruses. So as far as I'm concerned, the legal stuff is more likely to infect your system with malware.
eli is referring to the binary downloaded from the website possibly containing malware. Not that the website might possible infect you through a drive-by-download.
For very weak values of "safely". If, for example, the app has an auto-update feature, like many apps have, then they can simply push malware onto you at some point down the road. Even if they don't have an official one, it wouldn't be too hard to hide one in the code.