OOppss.. stuck this in the wrong post before...
Don't keep trying to remove them like you are unless you want to snap the bolts and have to drill/tap to a larger bolt. What has happened is corrosion/rust has built up on the threaded portion of the bolt extending into the swingarm. By trying to remove it you are just mashing that crap into the fragile threads of the aluminum swingarm and will seize the steel bolt snapping it off.
I am not sure of the swingarm on the KX5, but most alum swings have small drain holes for water accumulation on the underside of the arms near the adjuster bolts. I am at work and don't have access to look at my KX5 to double check that info though.
Anyway, you need to either lay your bike on its side or remove the swingarm to remedy the situation. Make sure to elevate the front end up about two feet or so higher than the rear end.
First: If you don't have holes, drill some small 1/16 inch holes about a inch or so back from where you believe the bolt is exposed on the underside of the swingarm tubes. This will give you access for a spary nozzle tube to fit inside the arm bar.
Second: Spray alot of break free, wd40, anti-seize type lube into the swingarm until you are sure it is fully soaking the threaded portion of the bolt completely. Please be careful with an ignition source because the fume and liquid left behind will be very flammable. Let this sit for a least an hour if not overnight.
Third: Slowly remove the bolt out a few threads and then back in again to break the crud free. The bolt should come out easily and then all the crud will drain out through the bolt hole. YOu can put silicone over the hole when you are rebuilding the bike later to keep contaminants from reentering the swingarm.
Sly