I think I can convey oh-so-slight difference.
The first one implies imagination of the subject: "if I do it, they will be disgusted". Currently, the audience has not been aware such thing might even happen. It's a forethought of the subject taking expected reactions into account.
The other is about the audience already considering it: "I hope he doesn't try that, that would be disgusting!" - the act of forming opinion by audience is already realized. It's following the current public opinion, not just imagining the future one.
But the difference is moot due to "were" which implies neither thought happened actually.