Its clear from the link provided in the WP that the DC Mayor's office is waging psychological warfare on the protestors, not giving them enough places to pee.https://www.washingtonpost.com/dc-md-va/2021/01/06/dc-protests-trump-rally-live-updates/
They pushed past police barriers and by the standards of these protesters that almost certainly qualifies as "violent". Tear gas has been deployed.
"When you got to go, you got to go. But finding a spot to use the restroom on the Mall proved hard amid the protests." -- from the link provided
"'If you’ve ever watched a Trump rally,' they tend to be large, said one 50-year-old man who came in a group of six from Maryland. After about an hour, the man, who declined to give his name, was almost at the front of the line. 'And this one is pretty important,' he said." --also from the link provided
I always hate going to DC. Everything is freaking expensive, and you can never find a restroom when you're storming the halls of Congress, if you can even get there through all of the traffic. Simple bottles of water are expensive, and you can kiss your life savings goodbye if you don't bring a bag lunch.