zincwarrior, a copout? Really?
Do you suggest that pro-1A organizations should invite would-be book banners and book burners as keynote speakers?
Do you suggest that LGBT organizations should ask for speakers from Westboro Baptist?
It is not particularly common for advocacy groups to invite opposition speakers, unless they are hosting a debate. I don't care what issue you bring up, this will hold true.
So, again, if you can think of some pro gun Dems you'd like to have as speakers, try to get them.
If you really want to try to get Eric Holder, then you need to sell the NRA on the idea of a debate as a reason to hold an event.