I don't feel insulted, though I think I might do if I were 'wavering', in the sense of having serious questions about God, etc. I know a few people who have moved from agnosticism to Christianity, and in no case were they motivated by the fear of spending an eternity in torment.

they ought to think about how the evangelical adverts are viewed by non-believers.

Yes. I do. Every time I see one of them I cringe, because they're offensive, theologically dubious and, pragmatically speaking, stupid. Unfortunately I can't do anything about them, because 'believers', let alone 'Christians' aren't a homogenous block, any more than 'agnostics' or 'atheists' are.