On the radio, the author being interviewed is talking about the slaves used on seacraft. Huge numbers are used on ships. Black books are kept to make sure the true pay rate is kept hidden, and you are locked up, not allowed to leave.
And it's never mentioned, but most of them are men.
Most slaves in the modern world are men.

It's not seen as important - female slaves are far rarer but they get all the attention.Take a look at this BBC article. It will either use gender neutral terms - so you don’t realise it’s happening to boys and men - or it specify the gender - because a female is being hurt, and now you must feel sympathy for their oppression.

Boy slaves will only be called ‘children’.

http://www.dw.de/report-estimates-30-million-people-worldwide-living-in-slavery/a-17164558

The males cannot be victims! They are victimisers. That is feminist doctrine. So their masculinity must be erased.

We care when women suffer. We used to care about men, too. #Feminism changed all that.
Men crying? They need to man up. Or we'll drink a cup of their tears.

The feminist vision of the future is HeForShe. He exists to labour for her. She to be carried by him, to be worshipped by him, returning only contempt and violence.

It is slavery.

Worse, it is slavery of the mind, enforced by the slaves in their self-loathing.

The abused in love with their abusers. The abused enforcing the abuse.