The Antisocial Socialist

I'm not sure if you're replying to the right person? I'm not reading this phrase from an American perspective and most of the criticism I've seen about these t-shirts is not coming from that perspective either (and reading it that way, the slogan would make very little sense). (I'm not being sarcastic about this, I think someone else here interpreted it that way but that wasn't where I was coming from.)

The issue is that in the context of this movie and this promotional campaign (for the reasons I've pointed out), the phrase comes across as tone-deaf -- the British empire had issues with slavery and after that, with identured labour (both of which were associated with racism and colonialism).

This article does a good job of explaining in a simple way that while anti-slavery activism was an early platform for women activists, a lot of the language and imagery used wasn't free from crappy power dynamics and also appropriated the experience of slavery to talk about the experiences of women who weren't slaves.

Quote from that:

Simply put, freedom for the enslaved woman is not the same as freedom for the white, British woman. It was defined differently, and relied on different conditions. It seems very obvious, or it should be obvious, that enslaved women dealt with oppression and sexism very differently. You don’t need to pick up The History of Mary Prince to know that, but maybe we should send the Suffragette actresses a copy.

For Pankhurst or Streep to call themselves slaves is incredibly tone-deaf to this history. The feminist language of Pankhurst’s time had a troubling tendency to appropriate the language of slavery. As another example, look at Charlotte Brontë’s Jane Eyre, a narrative with themes of female empowerment that features a protagonist whose voice uses elements of the slave narrative. White women did not experience slavery, and their use of the word “slave” is incredibly offensive to those who were enslaved.

Even if we give the early activists a "pass" on the grounds that there was less awareness, etc. etc., I don't think that really applies to the 21st century.

EDIT: To clarify, I don't really have a dog in this fight since I'm not very invested in that movie either way (and I'm not American or British), but I can see where people who have issues with that phrase within a British context are coming from, and I think they have a good point.