Not at all a safe assumption. Most importantly, it's not that uncommon for even less experienced Mac users to copy and paste Terminal commands to solve one problem or another. A lot of those "Just type this!" solutions I've seen involve sudo somewhere.
But on top of that, maybe I don't understand your meaning here, but do you do a security audit on every line of every script that you ever run? Especially scripts that you run without sudo? I know that I don't.
Not even that. Lots of Mac help sites will include snippets of Bash code for the user to enter (say, something using rm to delete files the Finder is having trouble statting), and people will just enter those. You don't even need to do anything sneaky with the copy/paste process. Just offer some malicious code and expect the user to run it blindly since they wouldn't be coming to MacNoobHelp.com if they were capable of vetting for exploits.
But on top of that, maybe I don't understand your meaning here, but do you do a security audit on every line of every script that you ever run? Especially scripts that you run without sudo? I know that I don't.