Indeed once tailwheel trained, you friend will actually be a safer pilot since, even when flying a nosewheel aircraft, he will hold off correctly because of his tailwheel training. He will thus be far less likely to become one of those several pilots in the AAIB reports each month who break their aircraft's noselegs. Just watch the C172s and PA28s landing at GA fields - many will land on all 3 wheels together, with little or no attempt at a hold off.
I agree completely with all that. But this is my point:
Once airbourne the plane doesn't care where the nose wheel is so from a risk point of view they are the same. But are you seriously telling me that you aren't more likely to be involved in a take-off/landing accident in a taildragger than a nose gear aircraft?
If someone was trying to say: 'Taildraggers
are dangerous' then I'd be the first to stand up and correct him...because I don't believe they are and like you said, with proper training they are fine.
But danger and risk are relative terms as well and I think if I asked an instructor: 'Which is more likely to be involved in a landing or take off accident, a nose or tailwheel aircraft?' They would say tailwheel.