From the artist:
 
 
It occurred to me just how similar the two characters were, so I HAD to draw this.
 
Both were villains.  
Both were leaders of their own cult.  
Both had their own fair share of radical supporters.  
The radical supporters of said groups believed they were doing the right thing.  
Both characters employed heavily on banners, performances and parades to sway more newcomers to their cause.  
Both had the ability and power to take away the essential element of others (i.e. bending/cutie mark, the important part which gives power to the user/owner).  
Both managed to take away the essential parts of the protagonists as well later on.  
They committed these actions solely for their twisted version of equality.  
Both were hypocrites and liars, taking everyone’s elements but their own.  
Both were eventually exposed/unmasked with water at the end.
 
Additional information:
 
The writing on the poster is in Chinese, and it reads , meaning “Witness! Join the Revolution!”.
 
The Equalists’ symbol is a large red circle inscribed with the Chinese character , which can mean “equal”, “level”, or “peace”. This insignia is seen on many Equalist banners throughout the Legend of Korra series.