If memory serves, at least in the US this was the opposite. The free market was fine with serving least wing groups. It was the government that stepped in and told individuals to not be leftist, under threat of force.

Only then did businesses stop associating with those people, because the government was implicitly threatening them.

It was exactly the government's interference that caused the deplatforming of potential leftists during the red scare.

The government isn't an entity with its own independent will; the US public broadly voted in officials that put in place those policies. Leftists who openly identified as such faced all sorts of problems doing business even without government intervention.

Hollywood blacklists, the most famous example from the red scare, only began after HUAC subpoenaed and held people in contempt.

You're just repeating the same invalid argument. Go and look up the history of widespread small scale anti-lefist incidents in that era that occurred before the HUAC existed.

The onus is on you to provide examples. Most of what I know of, and what I can find documented, was government sanctioned or under (implied) threat of government retaliation.

Please cite examples of these widespread small scale, grassroots anti-leftist incidents.