It's not that complicated... Plant based = diet Veganism = philosophy
Can't really blame you for not knowing as they do get used interchangeably in the media.
But you can't just self identify as a person that follows a certain philosophy without actually following it. Vegans avoid cruelty towards animals and humans are animals.
I don't think you can stop cruelty through cruelty. Veganism is about acknowledging every individual and abstaining from exploitation and cruelty towards them. It's not some sort of utilitarian philosophy where it's ok sacrifice a small number of individuals for the good of a larger group.