They didn't refuse; they weren't given much time to comply. They had been there all day and were set up to render support to peaceful protesters.
My friend was at the periphery and took off when the tear gas started (ok, capsicum vapors or whatever the tech term is). But here is a detailed account of what happened. While I don't know the person who wrote it, it jibes with the facts as I have been able to determine them:
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"Friends, I am ok, but I am, frankly shaken. I was at St. John's, Lafayette Square most of the afternoon, with fellow clergy and laypeople - and clergy from some other denominations too. We were passing out water and snacks, and helping the patio area at St. John's, Lafayette square to be a place of respite and peace. All was well - with a few little tense moments - until about 6:15 or so. By then, I had connected with the Black Lives Matter medic team, which was headed by an EMT. Those people were AMAZING. They had been on the patio all day, and thankfully had not had to use much of the eyewash they had made. Around 6:15 or 6:30, the police started really pushing protestors off of H Street (the street between the church and Lafayette Park, and ultimately, the White House. They started using tear gas and folks were running at us for eyewashes or water or wet paper towels. At this point, Julia, one of our seminarians for next year (who is a trauma nurse) and I looked at each other in disbelief. I was coughing, her eyes were watering, and we were trying to help people as the police - in full riot gear - drove people toward us. Julia and her classmates left and I stayed with the BLM folks trying to help people. Suddenly, around 6:30, there was more tear gas, more concussion grenades, and I think I saw someone hit by a rubber bullet - he was grasping his stomach and there was a mark on his shirt. The police in their riot gear were literally walking onto the St. John's, Lafayette Square patio with these metal shields, pushing people off the patio and driving them back. People were running at us as the police advanced toward us from the other side of the patio. We had to try to pick up what we could. The BLM medic folks were obviously well practiced. They picked up boxes and ran. I was so stunned I only got a few water bottles and my spray bottle of eyewash. We were literally DRIVEN OFF of the St. John's, Lafayette Square patio with tear gas and concussion grenades and police in full riot gear. We were pushed back 20 feet, and then eventually - with SO MANY concussion grenades - back to K street. By the time I got back to my car, around 7, I was getting texts from people saying that Trump was outside of St. John's, Lafayette Square. I literally COULD NOT believe it. WE WERE DRIVEN OFF OF THE PATIO AT ST. JOHN'S - a place of peace and respite and medical care throughout the day - SO THAT MAN COULD HAVE A PHOTO OPPORTUNITY IN FRONT OF THE CHURCH!!! PEOPLE WERE HURT SO THAT HE COULD POSE IN FRONT OF THE CHURCH WITH A BIBLE! HE WOULD HAVE HAD TO STEP OVER THE MEDICAL SUPPLIES WE LEFT BEHIND BECAUSE WE WERE BEING TEAR GASSED!!!!
I am deeply shaken. I did not see any protestors throw anything until the tear gas and concussion grenades started, and then it was mostly water bottles. I am shaken, not so much by the taste of tear gas and the bit of a cough I still have, but by the fact that that show of force was for a PHOTO OPPORTUNITY. The patio of St. John's, Lafayette square had been HOLY GROUND today. A place of respite and laughter and water and granola bars and fruit snacks. But that man turned it into a BATTLE GROUND first, and a cheap political stunt second. I am DEEPLY OFFENDED on behalf of every protestor, every Christian, the people of St. John's, Lafayette square, every decent person there, and the BLM medics who stayed with just a single box of supplies and a backpack, even when I got too scared and had to leave. I am ok. But I am now a force to be reckoned with."
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Given that the Episcopalian Bishop in charge of the church allowed the protesters to be there all day, and immediately condemned Trump and his cabal for pushing them off and occupying the area without permission, any whiff of legitimacy for the White House's actions dissipates pretty quickly. The protesters and support personnel were welcome in the churchyard. TRUMP WAS NOT.