I am interested in the line of thought that if they want or wear bikinis at this age they will become more passive (someone said that - don't remember who) or that they will think less of themselves, or it will start a trend in how they dress.
Now - for example - me, circa 1979:
I loved that suit. It was hot pink, and had gold rivety things on the top, and a ruffle. I really and truly loved that suit - obviously since I still remember it, and I knew where to find it in the old picture albums. LOL
I don't feel that having this suit influenced my self perception, my passivity level, my self esteem or how I dress now. In fact now, I would be less likely to wear a bikini due to comfort reasons. I might do one of the sport ones, but not halter necks.
I understand all the reasons for not doing it - and I agree with a lot of them. Sun protection, too adult, impractical for wee ones, uncomfortable, want more modesty, skeeves you out...all valid reasons. But I think that projecting what the kid will do or be like due to a swim suit when they are a toddler is a bit of stretch. For the record I own neither hot pink clothing nor bikinis at this point in the game. LOL And most totally no gold rivety things in my clothing. LOL