"I figure I can design something that conveys a message we can all agree on"

Good luck with that... 'gordian knot' ... 'can of worms' ... 'herding cats' ... etc. :j

"find somewhere to post it on the web"

I suggest asking for a GL Garden page after the design is done. I wouldn't want to download something like that from a site I didn't trust.

"people can print off copies and leave them in various places for people to find and read."

It's worth doing, if it can be done right, and you're one person I believe can do it.

"I feel it’s best to tackle a narrow scope of issues in a single pamphlet."

Probably. It could, if you wanted, point the reader to the web site where the original can be downloaded so more copies can be made (in case it gets in the hands of someone who agrees with it), and that site could link to discussions of other topics, or other pamphlets, so there's no need for one pamphlet to cover everything.