The truth of the matter is, the St. Patrick's Day parade doesn't do much to improve the reputation of the Irish as anything but drunks (and heck they even ban gay Irish groups from marching in that parade, how's that for tolerance!), sexual harassment is fairly rampant at the Puerto Rican and West Indian day parades (which doesn't help the reputation of either group).
I've marched in the New York City pride parade (and I wore perfectly reasonable clothes, t-shirt and shorts). There's not much like having one million people cheering you as you march and having every important politician in New York a couple of hundred of feet in front of you (including Hillary). While there are some outlandish parts of the parade with dancing boys and Dykes on Bikes, most of it was pretty boring, like politicians, activists and social groups (like the gay rugby team). I really think the parades do show the breadth and depth of the gay community in New York City (from the crazy to the staid) and in other cities and it's an excuse to sit out in the sun and just have fun. I'll likely be marching again this year, handing out pamphlets to everyone I see trying to remind them of all the important work still to be done. If it weren't for the nerdy boys and girls who started the first gay rights groups in the 50s and the outrageous drag queens and flamboyant boys who taunted and jeered the cops at the Stonewall Inn in 1969, we might not even have progressed as far as we have today. I think we need them both. The flaymboyant boys get people's attention, the nerdy ones are willing to do the grunt work to achieve equality.