Looks like a gathering of hippie pinkos, +50 years.
The yellow and black signs are a tip-off that some Marxist group is behind them, usually the Stalinist “Workers World Party” and its’ front, IAC -International Action Center, ANSWER - Act Now to Stop War & Racism, or the Party of Socialism and Liberation (a WWP split off).
Sometimes their signs are Orange and Black. You’ve seem variations of them in Ferguson, Baltimore (Peoples Power Assembly, Blue and White), NYC, DC, Chicago, etc.
Now if anyone recognizes the old leftists in this photo, let us know. There have always been reds in Birmingham and a few university towns in Alabama, so from the looks of these people, they could be some of them. Or they could just be loony liberals with nothing better to do with their time, like house, feed, clothes, and educate Syrian refugees.