I actually just did a bit of reading about it. It seems to be an age based change and almost entirely in the USA. I guess it's just one those natural changes that happens to every language over time. This is just a pet peeve of mine.
The author didn't need to make Hayato a pedo. Can you imagine if western comic writers wrote like Japanese ones? Loise Lane would be a shotacon and Susan and Johnny Storm would be in an incestuous relationship.