While the current versions of "red flag" laws are wrong, the concept is correct. Just consider the most recent incident in the Texas church. This man was known to be mentally disturbed. If there had been a way to stop him prior to him walking into that service, there would have been three lives saved. Those two innocent victims had their right to live "infringed". Again, the current versions are wrong, but virtually every news worthy shooting event has been committed by an individual that was known to have mental issues.
The man was also a felon, he shouldn't have had access to firearms in the first place. So laws did not stop that shooting. And that is the crux. Those bent on obtaining a firearm will, those bent on killing people will, and not a single law will stop them. The ONLY way to protect people is to allow them to protect themselves. Any law that seeks to prevent a person from legally obtaining a firearm or removing that firearm without due process is unconstitutional.