I’m 100% sure they mean “kicking ass” in the physical sense.
Via The Blaze:
If you thought the unions might tone down their rhetoric to dispel reports that their members are unruly bullies, think again.
In exchange for a donation from their members, the Communications Workers of America (CWA) union is offering free bumper stickers, including one that proclaims: “KICKING ASS FOR THE MIDDLE CLASS!”
Extra credit: What suggestions do you have for their next bumper sticker? I’ll kick it off.
“We’re stomping skulls for the working class”