This was a thing in Denmark probably 20 years ago, now it's no longer legal to demand union membership for employees. But there was one incident 4 years ago where union members at Kastrup Airport tried to bully a coworker to join them. They even went on strikes three times because of this, with zero effect. Can't tell if the bullying is widespread though.

https://www.dr.dk/nyheder/penge/3fer-bag-trusler-og-boelleme...