A Syrian refugee who was shouted down at a Stop the War demonstration says he “felt oppressed” by the group.
The protest in Downing Street on Friday evening was against the American attack on a Syrian airbase.
Hassan Akkad, from Damascus, asked why the group was not protesting against President Assad instead, but was drowned out.
He said: “British people not letting a Syrian say something about Syria in a protest about Syria. It’s mad.”
The 29-year-old said he had wanted to be the voice of Syrians who were still in the country but left the protest “livid”.
Stop the War was founded in September 2001, after US president George W Bush announced a “war on terror”.
After a video of the encounter was shared widely online, Mr Akkad told the BBC: “I didn’t see them protesting against the chemical attacks, I didn’t see them protesting against Putin bombing Syria for the last two years.
“I wanted to go to that protest and I wanted to observe.
“I went to the protest and I saw a group of 30 people with placards, not a single mention of Assad.
“All the placards are against Donald Trump and they’re repeating baseless slogans with their megaphones.”
‘Literally shred people’
He added: “I went to them respectfully and said, ‘Listen I’m a Syrian refugee who lives here and I have an opinion, it’s a protest about Syria I want to say something’.
“They didn’t even address me, they ignored my existence. With their megaphones they went louder and louder and the organisers told them to carry on.”
Mr Akkad left Syria in September 2015. He says he was imprisoned twice and tortured for protesting against Assad’s regime.
He left his family there and made an 87-day journey to the UK.
Mr Akkad said when the US launched its attack on a Syrian airbase, it did so with “great accuracy” whereas, he said, Assad’s bombers “literally shred people down”.
“They [President’s Assad’s forces] have killed hundreds of thousands, we’ve lost our home, we were displaced, we were made refugees all because of the Assad regime,” he said.
‘Mute our voices’
“People were tortured to death, chemical attacks, all sort of attacks barrel bombs shredding children and flattening down entire cities.
“So bombing Assad’s war machines is in our favour because that means less Syrian civilians will die, less children will die.”
After the group would not let Mr Akkad speak, he said: “I felt oppressed, it was like being back in Syria. Like how the Syrian police used to mute our voices.
“I’m not going to be silenced I have the right to say what I believe.
“I left the protest. I was angry, I was livid.”
The BBC has contacted Stop the War for a response. On its Facebook page before the protest, it said: “The Stop the War Coalition condemns Donald Trump’s decision to launch attacks against Syrian targets.
“This action will only increase the level of killing in Syria, and inflame the terrible war that has already caused untold misery for the people of the country.
”This is the worst possible way to respond to the indefensible attack at Khan Sheikhun.
“As well as deepening the tragedy of the Syrian people, this utterly irresponsible act threatens to widen the war and lead the West into military confrontation with Russia.”
Video courtesy of Tehmoor Khalid.