If you're a vegetarian for ethical or environmental reasons, I'd think lab grown meat is probably totally ok to eat. If you're a vegetarian for health reasons, not sure why you can't eat meat a few meals a month?
Here's a train of thought to help illustrate:
I'm not vegan but I'm glad to eat lab-grow meat! Its clearly acceptable for {many reasons}.
Oh, how about meat grown from rats? Tasty and nutritious?
Uh, well, sure I guess.
How about grown from apes?
But...but...that's not...
And our new product: meat from people. Tastes like pork!
No, wait a minute, that's going too far!
The latest fad: meat from people you know! Your spouse! Your kids! Your grandmother!
Blech! I couldn't eat that!
Everybody has a different 'blech' threshold. And its all 'religion'.
What about just that I don't prefer the taste?
For instance, I would have no problem trying meat made in the lab from rats, apes or people.
But I probably wouldn't eat fish or goat or lamb, not because I have some"religious" reason for it.
If a religion can be defined as only a set of personal preferences, it seems like the entire concept of a religion is without a real clear boundary.
The other thing is that oyster farming improves water quality and the environment. So, vegans—go crazy I guess!