In a free democracy that values the right to peaceful protest, law enforcement and political leaders have to ask the best way to preserve that essential right for all citizens while keeping the peace. The question I would rhetorically ask—because the answer is fairly obvious—is whether sending poorly trained agents armed with lethal weapons and, apparently, improper instruction on probable cause to "keep the peace" achieves that end.
It's easy—and correct—to condemn acts of violence by protestors. But in a free democracy, we should hold the armed representatives of the people's government to a higher standard than we do a mass of protestors, among whom there are, no doubt, some provocateurs and law breakers.
This isn't an either/or proposition. One need not defend brick-throwers or arsonists in order to condemn arrest-without-probable-cause or the use of "less lethal" munitions against bystanders. That false dichotomy is what authoritarian regimes use to try to justify the wildly inappropriate—and, in the US, illegal—use of force to put down political opposition.
But even if we take that as a given, it seems to me that everyone wearing the same color clothing—and thus it being harder for the officers to distinguish protestors from each other—works against the probable cause argument, and not in its favor. I'm far from an expert on this, but my understanding is that in some (most?) applications of probable cause, individualized suspicion is a requirement; if officers are unable to distinguish protestors from each other, it seems like that would make it harder for them to meet the necessary standard to justify an arrest.
The argument that innocent protestors didn't make it easy for the police to distinguish them from criminals in their midst does not seem like it modifies the probable cause requirement; officers can't go around arresting (or, worse, using violence against) peaceful protestors simply because the officers are unable to easily identify the minority who are lawbreakers in their midst.
Portland Police has been catching and releasing these rioters for over 50+ days because the DA refuses to prosecute. The mayor is the police commissioner of Portland and he recently came out to stand with the people attacking federal law enforcement. The city council is even more radical than the mayor. The local government and state government have done nothing to suppress the riots and arguably are aiding and abetting the actions of a violent and vocal minority of citizens.
The omission of the recent history of the violent actions of many of the "protestors" in Portland is shocking to see. Only conservative news organizations are making any mention of what is going on. Outlets like CNN, ABC, NYTimes, WPost, etc. have been silent until the recent actions taken by federal law enforcement. When they have talked about now, the coverage has been anything but even handed and has veered into gaslighting and willful blindness. Anyone who tries to speak out about this on Twitter is attacked en masse. Unless you go looking for a different opinion, you likely have no idea what is really going on.