This is a popular saying among many nudists but I think it needs a bit of elaboration. After all, I consider myself a real nudist (I am most comfortably nude as I write this). So why the elaboration? I have tanlines. Maybe I am taking this a bit too far, but that's how I am, I love messing with words and other people's minds.
Over the last 2 weeks I was out and about in the UK, often with textile-toting friends in cities and zoos and so forth. The weather was great so I wore shirts with short sleeves and shorts. These two items got me beautiful tanlines on my arms, neck and legs.
A real nudist therefore can certainly have tanlines. I assume that the tanlines 'everyone' is referring to are those of bikinitops and swimming trunks etc. Still I couldn't leave it to bother you with this. I agree that a real nudist has no swimwear tanlines.