"Annoying vegans" are usually associated with baseless moral grandstanding by their detractors. Someone who meticulously cites their sources and allows those citations to do the arguing for him seems like the exact opposite.
FWIW, it's possible to be both a moral grandstander and meticulously cite sources: for example, consider a vegan who says it's morally wrong to kill animals (which, depending on your worldview, could be baseless), but also cites sources saying that eating meat is a bad choice for the environment (which is easily citable).