If we go too far with such arguments, we'll hit slippery slopes regarding such issues as "artistic expression", etc. Besides, today's kids are arguably exposed to worse within their own peer groups and through the mass media; in an age when 13-yr-old girls are (under)dressing (and according to tabloid journalism, behaving) like Paris Hilton, fat ugly old nude men at Pride is practically nothing. (But what do you want instead? Purdah?)
That said, I'd still advocate a token "PG-13" principle regarding Pride--but with the understanding that "protecting the kids" is really a smokescreen for "protecting the squeamish", which is a category that transcends age. And maybe we need such smokescreens; ultimately, it's only a matter of being responsible, but there's a leeway of definition as to what "responsible" is, and we must allow for that.
So yes, if I were a parent, I wouldn't be so blithe about Pride; yet my advice to the unprepared young'uns might be more in the way of disclaimers than outright prevention. It's like serving liquor at formal occasions; if one takes the European approach, the kids are free to try, but within limits, and if it disagrees with them, they have right of refusal. (And I'd rather be a "European" parent than a SUV-driving pasty white suburban hockey dad in the outer 905, for what it's worth.)
It's like the Spanish bullring; you must be prepared for what may be coming, period, regardless of whatever age you may be...