You avoided the primary question - what's the line them? It honestly doesn't even really matter, since the whole premise of your post is that there is a line and that you eventually have to strike and use force. Our only disagreement is where that line actually is.
Besides, acting like Portland was some grand victory is just silly. OK - the national guard is out of Portland for the moment. They just moved on to their next target. They flood the zone and move fast so the legal system can't keep up. The damage was already done and they just moved to sow chaos in a new location with a different militarized force. What a win.
Peaceful protests are an important tool to the fight, but these people only fear consequences. Physical, emotional, reputational or financial harm. It's a multi-faceted fight, but that's what it is - a fight. If they think they can best you through physical force alone, that's what they will do. You can't let them think that. You need a stick to respond in kind with.
Maybe you should read up on the Hindustan Socialist Republican Association or the Indian National Army. They both played major roles in Indian independence. Ghandi is a great story, but guess who he had as a counter balance? The stick.