The difference between this being done legitimately and illegitimately is not one I can put into words[0], but I would note that there are ways this can be legitimate in any society — the police, in a democracy (sometimes described as fancy mob rule), where the protection money is normally called "taxes" — and that quite a lot of countries are stopping people from doing business with Russia right now as part of a protest against what they're doing in Ukraine.

Unions have whatever powers they've been allowed to have by the country they operate in, just as do corporations and police forces.

[0] Where you put the line between balancing the powers of unions vs. corporations is one of the major political dividing lines for the last 175 years, I'm not going to do it justice.