A pimp takes money from people (often women) who make money from working (often in this case sex work). They do so by claiming to offer protection.
A trade union takes money from workers. They do so by claiming to offer protection.
A pimp gets very rich from taking the money, and often (one suspects) does no more than drive around.
Trade union bosses become very rich (many earn over £100,000 per year plus expenses), and one wonders if they do very much for this pay. Most seem to spend most of there time going on TV doing interviews.
Many unions seem to openly disagree with other unions.
I have over the years had several jobs, and it often amused me how the trade union representative, would always tell e how there union was the correct one and the others were dreadful.
It has also been over the years, rather entertaining to see on TV Labour MP’s brown nose trade unions, probably because they get so much money from trade unions. One often suspects that if a trade union leader were to enter a building with muddy shoes, that there would be at least one Labour MP who would fall instantly to the floo and lick the boots clean.