Social Identity Theory

So I was having a really interesting discussion with a colleague about what classifies under the bracket of social identity.
I came up with race, class, gender, sexual orientation, religion, ability/disability, and age. He added national origin.

Then I started asking him questions like, what about people who are smokers, or left handed, or vegetarian, or war veterans...we went back and forth, and he finally gave me a new concept to think about: there is an unstated hierarchy of oppression. But it is unstated because then it puts oppressed groups in comparison mode...and when comparison mode starts happening, subjectivity obscures.

I wasn't compelled in a theoretical/intellectual way that smokers, lefties, vegetarians, and war veterans aren't considered social identities, because the hierarchy of oppression proves to be a subjective matter. But in a functional way I am compelled...but perhaps only because I am socialized to think that way? lol

Almost makes me want to go back and finish my doctorate! But I saw a t-shirt today that does tend to describe my approach to academics: