It is better than taking no action and letting a dangerous individual keep his firearms and bring them to bear to shoot up a family or school.
The world is not perfect. Sometimes, in an emergency, you have to diffuse the situation first, and sort it all out later.
I continue to be surprised at the reflexive opposition to red flag laws. Among the "gun control" measures being currently touted, they alone are directed at the nut who fires the gun, not just guns in general. The old saw is that guns don't kill people, people kill people. Well, fine - but then you resist even measures targeted at the people who kill people, just because they involve the precious subject of guns.
Selfishness, pure selfishness.
You seem to be missing that posting any threat to engage in such nefarious acts is a crime in and of itself.
Making credible threats to engage in such mayhem is a crime. Conspiring with anyone else to do so is a crime.
QED, you have the means to stop such maniacs, who are telegraphing their intent via the internet and other means--and are being stopped using current law.
Looking at the recent events, and even now, the interdiction of such proclaimed intent to engage in such activity, without red flag laws, indicates that current laws are indeed adequate to the task if used.
Opening any Civil Right up to loss on the standard that someone says they think someone
MIGHT maybe do something, is to eviscerate that right based on nothing more than gossip.
If someone once found a picture of you in your childhood wearing anything which might have indicated a sympathy (maybe a souvenir kepi or a t-shirt with a Confederate Battle Flag on it) toward the South during the Civil War, by today's standards, that would indicate
racist sympathies, and you could be muzzled pending a hearing (at your expense) on whether or not you were going to engage in hate speech--after they took your keyboard away and injected botox into your vocal cords to keep you from saying racist things.
Essentially, that is how red flag laws treat gun owners.