I had chosen not to respond to this thread until I saw how it fleshed (unintentional pun) itself out.  Now that I have let me share my observations. 

Some folks responded with a kind and understanding tone, explaining that veggies can eat vegan but not the other way around, hence the request for vegan fare at the picnic.  To those people, Dave for instance, I thank you for being level headed and open minded.  Your statements are true, and well presented.

Some folks agreed with me, stating they too felt ostracized for the same reason I set forth.  To those people, I wish you the best of luck...and thank you for seconding my emotion.

The last group I will address here is the self-righteous, holier than thou, misinformed, aggressive @$$hole.  This group seems to be headed by Francesco, but there is another name or two I would add to this list.  In response to my initial inquiry Francesco chose to respond with:

Suit yourself.  A vegetarian is somebody that does NOT eat any
animal products at all.  Hence the term comes from vegetation which are all
plants.  If you eat any animal products (eggs and dairy) you are NOT vegetarian.

Let's consider all the ways this is wrong.
first of all, you begin with "suit yourself."  Clearly no room for discussion with this 'gentleman'.  He knows all and those who don't agree with him are better off going away.
Then he goes on to define vegetarianism...incorrectly.  Ask any other knowledgable person and they will define a vegetarian as one who abstains from eating animals, but DOES eat animal products.  How dare you tell me I'm not vegetarian?!?!  I am not in competition with you, you small minded, egotist.  I have followed a strict vegetarian diet since 1992.  I am happy with the lifestyle I lead and the choices I make, and I make no excuses for it.
i just chose to check out your profile on the meetup, which was created in 2007 and reads "I'm trying to go fully vegetarian, but need help cooking. :)"  Eff you!  In 1992, when you were still hanging off your mom's teet, I declared myself vegetarian, received the Moosewood Cookbook for my birthday from my older sister, and have eaten no meat since.  Your, i'll say it again, HOLIER THAN THOU attitude is precisely why people have a hard time relating to vegetarians.  i have had many non-vegetarians explain this to me over the years.  No one wants to feel as if they're being judged.  No one has any right to judge, least of all you, you overnight militant vegan.

To the organizers of this group I do suggest you take a long hard look at the tone presented by the group, and most particularly by some of its members.  I had hoped to be an active member of your group, but that clearly is not in the cards.  I wish you all the best of luck and hope for success in spreading the gospel, I just hope it is done in a fashion that doesn't alienate others. 

Thanks for your efforts.

Be well,
Jeff