Even if someone does get put on the watch list, it is a restriction of rights without any fair trial by a jury of peers. Even then, their "peers" might be questionable. I could imagine that in places like Dearborn they would be sung jury nullification to the max.
Nope, the real response is for the targeted population to arm up for immediate active shooter response and then retaliate when and where it it ethical to do so.
The demand for the criminalization of being armed is in fact, unethical retaliation. It shows the mindset of who the Democrats are really itching to go to war against.