“(Federal Trade Commission prosecutions including in some instances organized plots to withhold patronage or advertising, also of course DOJ AntiTrust Division)”
Except for Obamacare, there are no federal laws that require a person to patronize a certain business or for a company to buy advertising on a particular media outlet. Boycotts are legal and we are all free to boycott a business.
We aS individuals are free to buy or not buy Yes. But there can be antitrust and racketeering and conspiracy considerations when it comes to organizing or directing boycotts.