"' saying "smile" or "cheer up" is just like saying "hello" or "good morning/afternoon/evening" or even just politely smiling at someone. "
That's bollocks.
Now I'm too old and fat to be harassed by arsehole men in the street, none of the nice people who say hello who genuinely mean it ever say "cheer up love" or similar.
If someone says "hello" to me it's got a chance of being a nice greeting. If someone says "cheer up" it would make me want to say "fuck off".
When I was young and got daily harassment from men in the street, they would often say "cheer up love" (when they weren't commenting on my boobs or my appearance or saying inappropriate things). I have been told to cheer up hundreds of times by men, Never once, not once, by a woman in the street. It's not "hello". It's intrusive, said by men to - often younger - women and they fuck off.
And it doesn't matter what they say - men speaking to young girls in the street is not appropriate. It's not appropriate because there is a culture of men harrassing women and girls - even very young girls - and even if that specific man doesn't perceive he is doing this, it is not appropriate to normalise older men talking to unaccompanied young girls, it make the world less safe for the girls.
Men harassing girls in the street is a very real occurrence. As is sexual abuse. And no I'm not accusing that specific man int he van of sexual abuse, or imagining peados in the bushes. But our culture is one in which it is sadly very common indeed for teenage girls and women to be sexually assualted and raped - just look at the many threads on this where most female posters have experienced some form of abuse or harassment. Normalising men speaking to young girls in the street is normalising the behaviour of leery men who do this with dodgy intentions, and there are lots of them - the kind of men who speak to 9 year olds may not be interested in the 9 year olds per say, but they are often the same kind of men who would try to get me to stop and speak with them or even go off with them when I was on my way home from school as a teenager, or who would say inappropriate things to me about my boobs and appearance. Normalising contact between strangers and girls in the street is not OK.
Anyone who doesn't get this is either a man - and the nice men often don't have any idea of the sheer scale of harrassment girls and young women experience as it's so common we often don't bother to mention it - or women who grew up in areas with a small enough population for it not to be such an issue.
Or - people just want a row. If so can you please fuck off back to AIBU, and leave the rest of mumsnet for those of us who like to have a conversation that isn't about piling on the OP, yet again. [yawn]