Stating a fact or observation is not sexist by itself. The anecdotal data around me shows that the people with food intolerance and I won't eat X because someone in the newspaper misinterpreted a study have a even number of X chromosomes. To make sure there is balance - there is a lot of bronutrition in the opposite direction.
> I have yet to meet a person whose diet choices fall out of the range of rationality
Any person that observes religious restrictions - that is not rational. Also any person that refuses to eat X based on pseudo, improperly conducted or improperly understood science.
> I am vegan because I would rather not have had a sentient animal purposely killed for my meal - and it is a decision I came to after years of thought and consideration.
That will push you only to vegetarian. To go vegan you need more reasons.