A lot depends on why the given person is vegetarian. If they are one because of ethical or religious issues, you wouldn't expect them to serve meat as it would violate their conscience.
Also, if someone doesn't know how to cook meat properly, then I don't want them serving it. Too great a chance of undercooking it and making people sick, or over cooking it and producing shoe leather.
I see the point of this, however, non-vegans can eat a vegan meal but vegans can't necessarily eat a non-vegan meal. Also, many Roman Catholics will avoid meat on Fridays during Lent; so, if your party is on a Friday, that might be an issue.
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Also, if someone doesn't know how to cook meat properly, then I don't want them serving it. Too great a chance of undercooking it and making people sick, or over cooking it and producing shoe leather.