In addition, there is good evidence for vegan diets having a lower impact on the environment [1] and some evidence for health benefits [2]. For many vegans, their diet is not motivated solely by ethical concerns. So it's really not a good example for parent's parent :)

[1] https://josephpoore.com/Science%20360%206392%20987%20-%20Acc... [2] https://www.choosemyplate.gov/vegetables-nutrients-health