Vegans are judgmental
Of course, some vegans are. There are all kinds of people in every movement, and veganism isn’t an exception. But the personality of adherents to a movement doesn’t determine the validity of the ideology behind it. For example, if someone against racism is a bad person, that doesn’t mean we can justify racism because some non-racist people are mean. If we don’t like judgmental vegans, becoming a vegan and being the counter-example is the best we can do.