Just ignore it would be my advice. Family are always weird, it's just something you have to live with, and really, morally the guy is kind of in the right given that you're happily chowing down on some innocent creatures corpse, even if he was an arse about it.
Give it a day or two, find and offer him a vegan safe beer and bond over some shared interest, then give the guy some gentle ribbing over it if he's not the hyper sensitive thin skinned kind.
Maybe even work around it and show some support a bit. Share a vegan safe starter and dessert with the two of them, but set up a nice table outside with some candles and wine for their main so you can show your happy to support their choices, but the rest of your family aren't going to change their ways just because of it.
Be the bigger person basically.