This anti-mandate demonstration doesn't make that clear at all. The people there (who are not all NHS staff according to every report I've seen) do not make up a majority of the doctors and nurses in this country.
As of September 2020, there were 385,476 nurses, midwives and ambulance staff working in the NHS and as of January 2021, there were 123,813 doctors, so it's absolutely obvious that the people at this demonstration were nowhere even close to constituting a majority of the 500,000+ NHS medical professionals.