When I first started keeping corals, green star polyps were robust, easy to care for and inexpensive. This screamed a good starting point for me, though as anyone has learned over time, this isnt a coral, this is a bloody weed!!!

A small section I picked up that once was about 2"x2" has encrusted on a large 10 odd lb rock, its now more like 10"x8" after I've cut away what I can to stop it from spreading.

Now soft corals will release chemicals when stressed, however I dont want anything ruining the rock, can i remove this rock and well... destroy this weed and save a nice rock, I dont want to have chemicals leech into it released from the coral if i would shut it off from light, nor do I want to scrub it off with a strong tool just to see it grow back.

Do I have any options or should I just crush this thing with a hammer and try to sell frags of it? Could I even sell a frag of this nuissance? If I can, will I even make enough to replace the rock that its on? I've kept small mats in the corner of my sand bed, in total i have probably 1.5 odd square feet of this and i want it gone but I would rather not destroy it unless its the only real option.

Do you want it all gone? If so, your best bet is to just take the entire rock out and do something to kill it or get it off the rock. Just keep in mind that if you want to keep the rock and be able to put it back in the tank, you need to make sure that whatever you do isn't going to be toxic to your tank inhabitants.
Also, if you think that GSPs are a weed, do not put xenia in your tank, because they are a pain in the but. I just had to cut one off of my big central rock in my nano cube so it wouldn't get too close to my acan. Then I tried to make a frag of it, but I'm not sure it will survive. Just FYI.

Yes, I've heard many warnings about xenia. I dont need ALL of this gone, but i would truly like to find a way to remove it from this rock. I have as noted several pieces ive pruned off over time and i have several rocks with a decent sized mat on them, so if I were to keep any, I would keep it on one of these small rocks so that I could keep it isolated from everything else.

So do GSP release horrible toxins? Is shutting this rock into a dark bucket for a month while doing water changes going to leave the rock in a usable form still?

Do you really want to keep the rock? It seems a shame to destroy them, it must look pretty nice by now, someone else would probably love it. I would have thought a store might swap the whole thing for another rock and something else.