This was defo a no win situation for the Seattle mayor, but she played it about as well as it can reasonably be expected.
Send in the goon squad and crack a bunch of skulls at the start of the protest and now you're a fascist and maybe someone dies there and its directly your fault. Protest movement is invigorated and surges.
Or
Back off and let human nature take its course, then come back in with cause as the clean up crew and blame the protesters for everything.
Partisans will partisan. I can already imagine in the first scenario the "Democrats are the actual fascists" and "watch this cute girl take a tear gas canister to the face" talking points that would be everywhere.
All told, well played.