Tag description Content contains one or more parties referring to themselves or others as objects rather than people, such as dildoes, toilets, or onaholes
note slight difference from say mind break or slavery or masochism.
There is already a proposal for the dehumanization tag
That said, there may be some differences between the two
I described the other one as a process rather than a state in itself
I second "dehumanization". It would be more exclusive and useful. Objectification is used broadly enough to also encompass people seeing relationships as just the price of sex, not engaging with their partner as a full person, only as a sexual object.