In that context, I understand the proposed ban on smoking. Having someone light up 3 feet away there is not much different from having someone light up at the next table in a restaurant. It'd ruin the whole experience for me.
That said, Sheep's meadow is one place at one time. There are a few more select spots with this type of outdoor population density: Screen on the Green...the north (and now south) sections of the Great Lawn on Shabbat afternoon. In any other context, a smoking ban seems, well, needlessly paternalistic. Times Square is more crowded on a regular basis. Shouldn't we ban smoking there first? Same goes for most NY city streets at commuting hours and at lunch. Same deal? If the reasoning can't be applied consistently in city ordinances, I say drop it. Heck,the expense of putting up no smoking signs in all the parks is enough to sully the notion in my mind.