Not wishing to speak for Clarks, but what I understand from what he says, is that both the choice of forum, to expound scientific theories, and his manner, are not appropriate to someone addressing a scientific question. He rubbishes others and so others feel free to rubbish him.
He is also selective: Why is Ioannides antibody test so marvelous and accurate, whilst that of the NHS so insenitive? Why on the one hand say that antibody tests are not reliable as a test of immunity, but then relies on only one set of figures. This is just one of internal inconsistencies he makes. He also proposes a theory, that about 30% of people have an innate immunity to the virus, purely by extrapolation of unconnected findings, all coated with a sheen of plausibility. Unfortunately he targets people like you (no offence to you) who seek wider knowledge and want to explore alternatives, but without the necessary knowledge to understand his methods and errors. This type of scientist can be dangerous for exactly this reason.