A protester who ignored staff's request to wear a mask threw a glass at the bar after being advised the venue didn't accept cash.

The man was among a crowd of anti-vaccination mandate protesters who made their way to the brewery after the march to Parliament House.

BentSpoke founder Richard Watkins said while everyone had the right to protest the mistreatment of staff was unacceptable.

"They don't understand the rules that are in place in Canberra and unfortunately that put our staff in a very difficult position," Mr Watkins said.

"At times, it was quite volatile.

"The staff handled things exceptionally well and to their credit served everyone and treated everyone equally.

"But unfortunately, the protesters didn't treat us equally."

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Mr Watkins said he had expected to see more police around busy Lonsdale Street on Saturday night, given thousands of frustrated people had made their way to Canberra.

"We are appreciative of what the police do, but if we are having big protests in town and people aren't going to do the right thing, we need some support," he said.

"We can't be expected to have to deal with these situations on by ourselves."

Police estimate around 10,000 people heard the call to rally in Canberra on Saturday, disrupting traffic in the morning with a march across Commonwealth Avenue Bridge before converging on the lawns of Parliament House where they remained for most of the afternoon.

Mr Watkins said generally those who made their way to BentSpoke had complied with directions from staff to wear masks to the bar.

He said despite the hostility shown by the individual who threw the glass, locals had stayed on to support them in their decision to stay open.

"All our locals got behind us and still supported us even though it wasn't a great climate to come and enjoy a beer," he said.

"We wanted to stay open for them more than anything."

Police have advised protesters they are no longer welcome at Exhibition Park from Sunday, as preparations get underway for the Canberra Show, which will be held at the Mitchell venue from February.

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