I believe we have reached the point where BLM and Antifa have done enough to be labelled as domestic terrorists. But until those now willing to take a knee are convinced, such actions will only inspire more to violence, not fewer.
What hard action would you have him take?
Military sweeps would, sooner or later, have to return fire--the "peaceful protesters" are increasingly armed thugs.
Were that to happen, the dead of Kent State would be invoked to rise and smite the "evil POTUS", in virtually every form of media.
As in the past, those caught in such sweeps could claim they were not participants, and would be released, as were thousands in the past.
And if any children were so much as scratched, (and they are there, being used as human shields, at least in the Stone Mountain protest where the group was heavily armed) cries of wounding babies (or worse) would ring worldwide, and those "crimes against humanity" would be played in every (heavily Communist) UN cadre gathering ever.
The present targeted arrests of those there is sufficient evidence to hold is about the only tool open to use which would not incite an even larger problem, propelled by the MSM propaganda machine.
Like the virus, this thing must burn itself out, and can only be contained or mitigated where the patients are willing to do what it takes.
Some are immune to the direct cognitive effects of this disease. Others have 'herd immunity', in that the vast majority will not allow the sickness to take hold in their community.
In this case, the patients are those who live in the affected enclaves and their leadership, and they have shown themselves unwilling to even speak up for the measures needed by their local governments, or if in those governments, unwilling to undertake those measures, some even going so far as to aid and abet the criminals, through action or inaction, instead choosing to side with the very pathogens destroying their towns.
One of the tricks of any insurgency is to provoke the existing (and, in this case, legitimate) government into acts of aggression and/or reprisal which can be portrayed in such a fashion that the existing government can be presented as evil in the eyes of the general population.
It is a ticket to sympathy, to cooperation, and to support from the masses. It is a way to "win hearts and minds". It is an old Communist tactic, and a fall back position when the simple balance of "haves and have-nots" isn't sufficient to provoke class war and ideology isn't winning through.
In America everyone wants to be a "have", but most recognize the way to become one is still not through the Communist concept of "equality" (where all are treated equally, but very badly), with no other means of rising above that except within the Party, and that rise can be just as fatal as being a nobody.
We have a better way, through education, hard work, or the implementation of bright ideas and better mousetraps. I believe most Americans still believe in that American Dream.