The rubber bumpstop is usually destroyed (do you see any rubber here?) and frozen on. Though the bumpstop's mounting stud keys into the arm to prevent it from spinning, trying to wrench off a rusty one like ours will often egg-out the mounting hole in the control arm. Use a wrench to keep it from spinning, although it's not necessary to find a wrench as rusty as ours. Sometimes if they're really frozen, it's best to grind through the stud's head with an angle grinder.