Quoted By:
First off, ero doesn't necessarily mean undies as clothes or hugely revealing stuff (I think we should agree than when it comes to lolita, Kana is in a category of her own...). To me, any style can become ero, when you have a bold element or two (shorter skirt, lower neckline, garters, corset etc...) and it can still look more modest than stuff that people wear on a Saturday night...
Now as to whether people should wear it in public... well that is their prerogative. As long as it doesn't break public decency laws I don't see why not. But I think for a lot of lolis this also depends on where they live, where they are wearing it to and so on... Like, I wouldn't wear ero if I am in the small village where my grandparents live, cause I think I would only draw negative attention and old ladies would faint and clutch their pearls in the street. But I live in a big city, and I often see girls in corsets and fetishwear on the weekends, so ero doesn't stand out that much here on a weekend night out...