The Constitution lays out the rules with which our government is bound. In the area of free speech and self defense they want to do an end run around the Constitution. Instead of following the rules laid out in the Constitution for amending the Constitution they want that power to lay in the hands of congress, in short ignoring the Constitution outright. The plain language found in the Constitution is ignored.
Even in the event the Constitution were to be amended, I would have issues with their goals. The freedoms described in the first two amendments are fundamental human rights, granted not by a government, but God. The right of freedom of association, speech, and thought and right to defend oneself is inherent in all Creation. Even were the Constitution legally amended in these areas I would not follow or submit to the changes.
Other rights defined in the Bill of Rights are perhaps less so fundamental human rights, and were they to go about amending the Constitution to remove them I would fight against the change, but once amended I would follow the change. Certainly I might try to change them back to the original, but I would work within the system to change them.