Why do FAR LEFT EXTREMISTS want to change the constitution?

ect, they want a new bill of rights that tells you what the government can do. Is that just another way of giving the already obese government more whoppers to down? Their excuse is that the constitution was made by a bunch of racist guys in white wigs who liked stretchy pants so therefore it doesn't matter. If you try to change the infrastructure of a skyscr without referring to the blueprint it will collapse. The same goes for nations.