The organizer's statement of, "People are also encouraged to utilize (their) second amendment right at this event just (in case) our first amendment comes under the much anticipated attack," the event's Facebook page says" is different from "let's all come armed looking for a violent confrontation." The organizer's statement does not constitute as incitement and incitement is the only speech exception I can think of at the moment to support the notion the 1st Amendment Free Speech Clause may not offer any refuge to the organizer's speech/conduct.
It isn't incitement (it's headed in that direction), but it isn't exactly peaceful by any means. I'm aware these people live in a right-wing bubble and are wholly incapable of understanding how an armed protest in front of your Community Center could be a bit intimidating.
Imagine the the outrage of an armed Islamic protest outside a Baptist Church in Phoenix. Muslims blaspheming Jesus while open carrying guns.
There is outrage from the right-wing if Muslims want to build a Mosque! Don't hear shit from the right-wing about the first amendment when those protests start up against the building of a Mosque.