Ex bicycle mechanic here: first, take the wheel and fender off to give yourself more room to work. Penetrating oil may work if it's available. Heating the bits with a torch (avoid the frame itself as much as possible) has done wonders for stuck parts but may cause visual damage to the surrounding paint. All else fails destructive removal may be required: either drill the bolt out, cut the top/bottom plates on the kickstand (careful not to nic the frame), or if you can find something that fits: cut the bolt through the middle once the wheel and fender are out of the way.